Cathode active materials for lithium-ion batteries

ABSTRACT

Compounds, powders, and cathode active materials that can be used in lithium ion batteries are described herein. Methods of making such compounds, powders, and cathode active materials are described.

CROSS-REFERENCE TO RELATED APPLICATIONS

The present application is a continuation of U.S. patent applicationSer. No. 15/458,618, entitled “Cathode Active Materials for Lithium-IonBatteries,” filed on Mar. 14, 2017, which claims the benefit under 35U.S.C. §119(e) of U.S. Provisional Patent Application Ser. No.62/307,956, entitled “Surface-Modified Cathode Active Materials forLithium-Ion Batteries,” filed on Mar. 14, 2016, and U.S. PatentApplication Ser. No. 62/307,964, entitled “Cathode Active Materials forLithium-Ion Batteries,” filed on Mar. 14, 2016. The content of eachapplication is incorporated herein by reference in its entirety.

U.S. GOVERNMENT LICENSE RIGHTS

This invention was made with U.S. government support under WFO ProposalNo. 85F59. This invention was made under a CRADA 1500801 between AppleInc. and Argonne National Laboratory operated for the United StatesDepartment of Energy. The U.S. government has certain rights in theinvention.

FIELD

This disclosure relates generally to batteries, and more particularly,to cathode active materials for lithium-ion batteries.

BACKGROUND

A commonly used type of rechargeable battery is a lithium battery, suchas a lithium-ion or lithium-polymer battery. As battery-powered devicesbecome increasingly small and more powerful, batteries powering thesedevices need to store more energy in a smaller volume. Consequently, useof battery-powered devices may be facilitated by mechanisms forimproving the volumetric energy densities of batteries in the devices.

Lithium transition metal oxides can be used in cathode active materialsfor lithium-ion batteries. These compounds can include lithium cobaltoxide or derivatives thereof. These compounds can be in the form ofpowders.

SUMMARY

In a first aspect, the disclosure is directed to a compound according toFormula (III):

Li_(α)Co_(1−x)M_(x)Al_(γ)O_(δ)  (III)

wherein M is B, Na, Mn, Ni, Mg, Ti, Ca, V, Cr, Fe, Cu, Zn, Al, Sc, Y,Ga, Zr, Mo, Ru or a combination thereof, 0.95≦α≦1.10, 0<x<0.50,0≦γ≦0.05, and 1.95≦δ≦2.60.

In some aspects, M is Mn, Ni, or a combination thereof, 0.95≦α≦1.10,0<x<0.50, 0≦γ≦0.05, and 1.95≦δ≦2.60.

In another aspect, the disclosure is directed to a powder comprisingparticles. The particles include the compound according to Formula(III).

In another aspect, the disclosure is directed to a powder comprisingparticles that have a core and a coating. The coating is disposed overat least a portion of the core. The core includes a compound selectedfrom the compound of Formula (I), Formula (IIa), Formula (IIb), andFormula (III):

Li_(α)MO_(δ)  (I)

(x)[Li₂M¹O₃].(1−x)[LiM²O₂]  (IIa)

(x)[Li₂M¹O₃].(1−x)[Li_(1−y)M²O₂]  (IIb)

Li_(α)Co_(1−x)M_(x)Al_(γ)O_(δ)  (III)

wherein,when the compound is Formula (I),

M is selected from Co, Mn, Ni, and a combination thereof,

0.95≦α≦2, and

1.95≦δ≦3;

when the compound is Formula (IIa),

0≦x≦1,

M¹ is selected from Ti, Mn, Zr, Mo, Ru and a combination thereof, and

M² is selected from B, Na, Mg, Ti, Ca, V, Cr, Mn, Fe, Co, Ni, Cu, Zn,Al, Sc, Y, Ga, Zr, Mo, Ru and a combination thereof;

when the compound is Formula (IIb),

0≦x≦1,

0≦γ≦1,

M¹ is selected from Ti, Mn, Zr, Mo, Ru and a combination thereof, and

M² is selected from B, Na, Mg, Ti, Ca, V, Cr, Mn, Fe, Co, Ni, Cu, Zn,Al, Sc, Y, Ga, Zr, Mo, Ru and a combination thereof; and

when the compound is Formula (III),

0.95≦α≦1.10,

M is selected from B, Na, Mn, Ni, Mg, Ti, Ca, V, Cr, Fe, Cu, Zn, Al, Sc,Y, Ga, Zr, Mo, Ru and a combination thereof,

0<x<0.50,

0≦γ≦0.05, and

1.95≦δ≦2.60.

In some aspects, the compound is Formula (I), M is selected from Co, Mn,Ni, and a combination thereof,

1≦α≦2, and2≦δ≦3.

In some aspects, the compound is Formula (IIa),

0≦x≦1,M¹ is selected from Ti, Mn, Zr, Mo, Ru and a combination thereof, andM² is selected from B, Na, Mg, Ti, Ca, V, Cr, Mn, Fe, Co, Ni, Cu, Zn,Al, Sc, Y, Ga, Zr, Mo, Ru and a combination thereof.

In some aspects, the compound is Formula (IIa), and 0<x<0.10.

In some aspects, the compound is Formula (IIb),

0≦x≦1,

0≦γ≦1,

M¹ is selected from Ti, Mn, Zr, Mo, Ru and a combination thereof, and

M² is selected from B, Na, Mg, Ti, Ca, V, Cr, Mn, Fe, Co, Ni, Cu, Zn,Al, Sc, Y, Ga, Zr, Mo, Ru and a combination thereof.

In some aspects, the compound is Formula (IIb), and 0<x<0.10.

In some aspects, the compound is Formula (III),

0.95≦α≦1.10,

M is selected from Mn, Ni, and a combination thereof,

0<x<0.50,

0≦γ≦0.05, and

1.95≦δ≦2.60.

The coating comprises an oxide material, a fluoride material, or acombination thereof.

In some aspects, the core includes a compound according to Formula(IIa). In some aspects, the core includes a compound according toFormula (IIb).

In some aspects, the core comprises a compound according to Formula(III). In further variations, 0.001≦γ≦0.03.

In one aspect, the disclosure is directed to a compound represented byFormula (IV):

Li_(α)Co_(1−x)Mn_(x)O_(δ)  (IV)

in which 0.95≦α≦1.10, 0≦x≦0.10, and 1.90≦δ≦2.20.

In a further aspect, 0<x≦0.10.

In a further aspect, the disclosure is directed to a compoundrepresented by Formula (IV), wherein 0.98≦α≦1.01.

In a further aspect, the disclosure is directed to a compoundrepresented by Formula (IV), wherein 1.00≦α≦1.05. In a further aspect,0≦x≦0.10.

In a further aspect, the disclosure is directed to a compoundrepresented by Formula (IV), wherein 0.95≦α≦1.05 and 0.02≦x≦0.05.

In a further aspect, the disclosure is directed to a compoundrepresented by Formula (IV), wherein 1.01≦α≦1.05 and 0.02≦x≦0.05.

In a further aspect, the disclosure is directed to a compoundrepresented by Formula (IV), wherein 0.95≦α≦1.05 and x=0.04.

In a further aspect, the disclosure is directed to a compoundrepresented by Formula (IV), wherein 1.01≦α≦1.05 and x=0.04.

In a further aspect, the disclosure is directed to a compoundrepresented by Formula (IV), wherein 0.98≦α≦1.01 and x=0.03.

In a further aspects the compound has the structure of Formula (Va) orFormula (Vb):

(x)[Li₂MnO₃].(1−x)[LiCoO₂]  (Va)

(x)[Li₂MnO₃].(1−x)[Li_((1−y))Co_((1−y))Mn_(y)O₂]  (Vb)

wherein 0≦x≦0.10, and optionally 0≦y≦0.10. In some variations, 0≦y≦0.10.

In some aspects, the disclosure is directed to a powder comprisingparticles, the particles comprising the compound represented by Formula(IV): Li_(α)Co_(1−x)Mn_(x)O_(δ). In various aspects, 0.95≦α≦1.10,0≦x≦0.10, and 1.90≦δ≦2.20. In various aspects, 0.95≦α≦1.10, 0≦x≦0.10,and 1.90≦δ≦2.20. In some embodiments, at least a portion of theparticles have a smooth surface. In various instances of theseembodiments, at least a portion of the particles have a tap densityequal to or greater than 2.2 g/cm³. In various instances of theseembodiments, at least a portion of the particles have a smooth surfaceand a tap density equal to or greater than 2.2 g/cm³.

In another aspect, the disclosure is directed to a cathode activematerial that includes the powders as described herein.

In a further aspect, the disclosure is directed to a cathode having thecathode active material disposed over a current collector.

In another aspect, the disclosure is directed to a battery cell thatincludes an anode having an anode current collector and an anode activematerial disposed over the anode current collector and the cathode.

In another aspect, the disclosure is directed to a portable electronicdevice including a set of components powered by the battery pack.

In another aspect, the disclosure is directed to a method for making apowder described herein. First, a precursor solution (e.g., an aluminumsalt and/or fluoride salt precursor) is prepared by dissolving theprecursor in a solvent to form a precursor solution. The precursorsolution is added to a particle powder to form a wet-impregnated powder.The wet-impregnated powder is heated to an elevated temperature to forma particle having the composition described herein.

In another aspect, multiple precursors (e.g., aluminum salts andfluoride salts) are dissolved in first and second solvents to form firstand second solutions, respectively. First and second solutions are thencombined to make a precursor solution, which is then added to particlesas described herein.

In another aspect, the disclosure is directed to making the particles bydry blending methods. Particles of a nanocrystalline material arecombined with particles comprising the compound of Formula (IV). Thenanocrystalline material particles and the particles comprising Formula(IV) are subject to a compressive force, shear force, or a combinationthereof. The nanocrystalline material particles bond to the surface ofthe powder particles. The particles thereby form a coating on the powderparticles.

In another aspect, the disclosure is directed to compounds representedby Formula (VII) or Formula (VIII):

Li_(α)Co_(1−x−y)M_(y)Mn_(x)O_(δ)  (VII)

Li_(α)Co_(1−x−y)Al_(y)Mn_(x)O_(δ)  (VIII)

When the compound is by represented by Formula (VII), in variousaspects, M is at least one element selected from B, Na, Mg, Ti, Ca, V,Cr, Fe, Ni, Cu, Zn, Al, Sc, Y, Ga, Zr, Mo and Ru. In some variations,0.95≦α≦1.30, 0<x≦0.30, 0≦y≦0.10, and 1.98≦δ≦2.04. In various aspects,the compound is a single-phase compound with an R3m crystal structure.In further aspects, α>1+x and/or α<1+x.

In further aspects, the disclosure is directed to a powder comprisingparticles. The mean diameter of the particle can be at least at least 5μm. In some aspects, the mean diameter of the particle can be at least20 μm. In some aspects, the particle can comprise secondary particles,each of which comprises a plurality of primary particles sinteredtogether. In some variations the at least 30% of the average secondaryparticle is formed of a single primary particle.

In further aspects, the disclosure is directed to a cathode activematerial comprising the compounds or powders.

In further aspects, the disclosure is directed to a battery cellcomprising an anode, a cathode comprising a cathode active material. Insome aspects, the battery cell can have a first-cycle discharge energygreater than or equal to 750 Wh/kg. In some aspects, the battery cellcan have an energy retention greater than or equal to 70% after 10charge-discharge cycles.

In some aspects, the battery cell can have an energy capacity retentionis at least 65% after 52 discharge cycles.

BRIEF DESCRIPTION OF THE DRAWINGS

The disclosure will be readily understood by the following detaileddescription in conjunction with the accompanying drawings, wherein likereference numerals designate like structural elements, and in which:

FIG. 1 is a top-down view of a battery cell in accordance with anillustrative embodiment;

FIG. 2 is a side view of a set of layers for a battery cell inaccordance with an illustrative embodiment;

FIGS. 3A-3C are a series of scanning electron micrographs showing,respectively, a base powder, a 0.1 wt. % AlF₃-coated base powder, and a0.1 wt. % Al₂O₃-coated base powder, according to an illustrativeembodiment;

FIG. 4 is a plot of data representing a performance of three coin halfcells, each incorporating a single cathode active material, during afirst cycle of charging and discharging, according to an illustrativeembodiment;

FIG. 5 is a plot of data representing a change in capacity, overextended cycling under rate testing, of the four coin half-cells of FIG.4, according to an illustrative embodiment;

FIG. 6 is a plot of data representing a change in capacity, overextended cycling under life testing, of the four coin half-cells of FIG.4, according to an illustrative embodiment;

FIG. 7 is a plot of data representing a change in energy density, overextended cycling under rate testing, of the four coin half-cells of FIG.4, according to an illustrative embodiment;

FIG. 8 is a plot of data representing a change in energy density, overextended cycling under life testing, of the four coin half-cells of FIG.4, according to an illustrative embodiment;

FIG. 9 is a plot of data corresponding to charge-discharge profiles foreach the four coin half-cells of FIG. 4 under rate testing;

FIG. 10 is a plot of data corresponding to charge-discharge profiles foreach the four coin half-cells of FIG. 4 under life testing;

FIG. 11 is a plot of data representing dQ/dV profiles for each the fourcoin half-cells of FIG. 4 under rate testing; and

FIG. 12 is a plot of data representing dQ/dV profiles for each the fourcoin half-cells of FIG. 4 under life testing.

FIG. 13 is a plot of data representing an influence of molar ratio on acapacity and efficiency of a cathode active material comprisingLi_(α)Co_(0.96)Mn_(0.04)O_(δ), according to an illustrative embodiment;

FIG. 14 is a plot of data representing an influence of molar ratio,represented by α, and Mn content, represented by x, on a c-axis latticeparameter of Li_(α)Co_(0.96)Mn_(0.04)O_(δ), according to an illustrativeembodiment;

FIG. 15 is a plot of data representing a change in the c-axis latticeparameter with molar ratio for Li_(α)Co_(0.96)Mn_(0.04)O₂, according toan illustrative embodiment;

FIG. 16 is a series of scanning electron micrographs of powder preparedat 900° C., 1000° C., 1050° C., and 1100° C., according to anillustrative embodiment;

FIG. 17 is a series of scanning electron micrographs showing aninfluence of temperature and molar ratio, α, on particle morphology,according to an illustrative embodiment;

FIG. 18 is a plot of data representing an influence of mixing ratio on acapacity and an efficiency of a cathode active material comprisingLi_(α)Co_(0.96)Mn_(0.04)O_(δ), according to an illustrative embodiment;

FIG. 19 is a series of scanning electron micrographs of cathode activematerials comprising Li_(α)Co_(1−x)Mn_(x)O_(δ) and prepared according toa co-precipitation method, according to an illustrative embodiment;

FIG. 20 is a plot of x-ray diffraction patterns of cathode activematerials prepared according to a co-precipitation method and comprisingLi_(α)Co_(0.96)Mn_(0.04)O_(δ), Li_(α)Co_(0.90)Mn_(0.10)O_(δ), andLi_(α)Co_(0.84)Mn_(0.16)O_(δ) with varying values of α, according to anillustrative embodiment;

FIG. 21 is a plot of x-ray diffraction patterns of cathode activematerials prepared according to a co-precipitation method and comprisingLi_(α)Co_(0.78)Mn_(0.22)O_(δ) and Li_(α)Co_(0.72)Mn_(0.28)O_(δ) withvarying values of α, according to an illustrative embodiment;

FIG. 22 is a series of scanning electron micrographs of cathode activematerials comprising Li_(α)Co_(1−x)Mn_(x)O_(δ) and prepared according toa sol-gel method, according to an illustrative embodiment;

FIG. 23 is a plot of x-ray diffraction patterns of cathode activematerials prepared according to a sol-gel method and comprisingLi_(1.131)Co_(0.90)Mn_(0.10)O₂, Li_(1.198)Co_(0.84)Mn_(0.16)O₂,Li_(1.241)Co_(0.78)Mn_(0.22)O₂, and Li_(1.301)Co_(0.72)Mn_(0.28)O₂,according to an illustrative embodiment;

FIG. 24 is a plot of differential capacity curves for cathode activematerials comprising LiCoO₂, Li_(1.05)Co_(0.96)Mn_(0.04)O₂,Li_(1.05)Co_(0.93)Mn_(0.07)O₂, Li_(1.110)Co_(0.90)Mn_(0.10)O₂ andLi_(1.19)Co_(0.72)Mn_(0.028)O₂ according to an illustrative embodiment;

FIG. 25 is a plot of voltage profile curves for cathode active materialscomprising Li_(1.05)Co_(0.96)Mn_(0.04)O₂, Li_(1.05)Co_(0.93)Mn_(0.70)O₂,Li_(1.110)Co_(0.90)Mn_(0.10)O₂, and Li_(1.19)Co_(0.72)Mn_(0.28)O₂,according to an illustrative embodiment;

FIG. 26 is a contour plot of discharge energy density that varies withMn substitution, Co_(1−x)Mn_(x), and lithium ratio,[Li]/[Co_(1−x)Mn_(x)], according to an illustrative embodiment;

FIG. 27 a contour plot of energy retention that varies with Mnsubstitution, Co_(1−x)Mn_(x), and lithium ratio, [Li]/[Co_(1−x)Mn_(x)],according to an illustrative embodiment;

FIG. 28 is a plot of differential capacity curves for cathode activematerials comprising Li_(α)Co_(0.99−y)Al_(y)Mn_(0.01)Oδ,Li_(α)Co_(0.98−y)Al_(y)Mn_(0.02)O_(δ),Li_(α)Co_(0.97−y)Al_(y)Mn_(0.03)O_(δ), andLi_(α)Co_(0.96−y)Al_(y)Mn_(0.04)O_(δ) according to an illustrativeembodiment;

FIG. 29 is a plot of differential capacity curves for cathode activematerials comprising Li_(0.977)Co_(0.97)Al_(y)Mn_(0.03)O_(δ),Li_(0.992)Co_(0.97)Al_(y)Mn_(0.03)O_(δ),Li_(1.003)Co_(0.97)Al_(y)Mn_(0.03)O_(δ), andLi_(1.014)Co_(0.97)Al_(y)Mn_(0.03)O_(δ), according to an illustrativeembodiment;

FIG. 30 is a plot of discharge energy versus cycle count for cathodeactive materials comprising Li_(0.992)Co_(0.97)Mn_(0.03)O_(δ),Li_(1.003)Co_(0.97)Mn_(0.03)O_(δ), and Li_(1.014)Co_(0.97)Mn_(0.03)O_(δ)according to an illustrative embodiment;

FIG. 31 is a plot of discharge energy versus cycle count for cathodeactive materials comprising Li_(α)Co_(0.98−y)Al_(y)Mn_(0.02)O_(δ),Li_(α)Co_(0.97−y)Al_(y)Mn_(0.03)O_(δ), andLi_(α)Co_(0.96−y)Al_(y)Mn_(0.04)O_(δ), according to an illustrativeembodiment;

FIG. 32 is a plot of nuclear magnetic resonance patterns forLi_(α)Co_(0.97)Mn_(0.30) and Li_(α)Co_(0.97)Mn_(0.03)O_(δ), according toan illustrative embodiment;

FIG. 33 is a plot of discharge energy versus cycle count for cathodeactive materials comprising Li_(1.01)Co_(0.97−y)Al_(y)Mn_(0.03)O_(δ) for0.077, 0.159, and 0.760 wt. % added Al₂O₃, according to an illustrativeembodiment

FIG. 34A is a scanning electron micrographs of particles of cathodeactive material prepared by firing a precursor and comprisingLi_(α)Co_(1−x−y)Al_(y)Mn_(x)O_(δ), according to an illustrativeembodiment;

FIG. 34B is a scanning electron micrograph of the cathode activematerial of FIG. 34B, but in which the precursor was fired at a highersintering temperature, according to an illustrative embodiment;

FIG. 35A is a particle size distribution of particles of cathode activematerial prepared from a precursor fired at 1050° C. and comprisingLi_(α)Co_(1−x−y)Al_(y)Mn_(x)O_(δ), according to an illustrativeembodiment;

FIG. 35B a particle size distribution of particles of cathode activematerial prepared from a precursor fired at 1085° C. and comprisingLi_(α)Co_(1−x−y)Al_(y)Mn_(x)O_(δ), according to an illustrativeembodiment

FIG. 36 is a plot of surface area change and energy retention versuscalcination temperature of a cathode active material comprisingLi_(□.01)Co_(1−x−y)Al_(y)Mn_(x)O_(δ), according to an illustrativeembodiment;

FIG. 37 is a plot of initial discharge capacity and coulombic efficiencyversus calcination temperature of a cathode active material comprisingLi_(1.01)Co_(1−x−y)Al_(y)Mn_(x)O_(δ), according to an illustrativeembodiment;

FIG. 38 is a plot of heat flow versus calcination temperature of cathodeactive materials comprising LiCoO₂, Li_(α)Co_(0.99)Mn_(0.01)O_(δ),Li_(α)Co_(0.98)Mn_(0.02)O_(δ), Li_(α)Co_(0.97)Mn_(0.03)O_(δ),Li_(α)Co_(0.96)Mn_(0.04)O_(δ), and Li_(α)Co_(0.93)Mn_(0.007)O_(δ)according to an illustrative embodiment;

FIG. 39 is a plot of c-axis lattice parameter versus lithium content, α,for cathode active materials comprising LiCoO₂,Li_(α)Co_(0.98)Mn_(0.02)O_(δ), Li_(α)Co_(0.97)Mn_(0.003)O_(δ),Li_(α)Co_(0.96)Mn_(0.04)O_(δ), and Li_(α)Co_(0.93)Mn_(0.007)O_(δ),according to an illustrative embodiment;

FIG. 40 is a plot of Raman spectra for cathode active materialscomprising LiCoO₂, Li_(α)Co_(0.96)Mn_(0.04)O_(δ), andLi_(α)Co_(0.93)Mn_(0.07)O_(δ), according to an illustrative embodiment;

FIG. 41 is a plot of discharge capacity after 52 cycles versus lithiumcontent, α, of cathode active materials comprisingLi_(α)Co_(0.96)Mn_(0.04)O_(δ), and Li_(α)Co_(0.93)Mn_(0.07)O_(δ),according to an illustrative embodiment;

FIG. 42 is a plot of differential capacity curves for cathode activematerials comprising Li_(1.025)Co_(0.96−y)Al_(y)Mn_(0.04)O_(δ), andLi_(1.00)Co_(0.93−y)Al_(y)Mn_(0.07)O_(δ), according to an illustrativeembodiment; and

FIG. 43 is a data plot of first-cycle charge capacity, first-cycledischarge capacity, and first cycle coulombic efficiency versus lithiumcontent, ca for cathode active materials comprisingLi_(α)Co_(0.96)Mn_(0.04)O_(δ), according to an illustrative embodiment.

DETAILED DESCRIPTION

The following description is presented to enable any person skilled inthe art to make and use the embodiments, and is provided in the contextof a particular application and its requirements. Various modificationsto the disclosed embodiments will be readily apparent to those skilledin the art, and the general principles defined herein may be applied toother embodiments and applications without departing from the spirit andscope of the present disclosure. It should be understood that thefollowing descriptions are not intended to limit the embodiments to onepreferred embodiment. To the contrary, it is intended to coveralternatives, modifications, and equivalents as can be included withinthe spirit and scope of the described embodiments as defined by theappended claims. Thus, the disclosure is not limited to the embodimentsshown, but is to be accorded the widest scope consistent with theprinciples and features disclosed herein.

As used herein, all compositions referenced for cathode active materialsrepresent those of as-prepared materials (i.e., “virgin” materials)unless otherwise indicated. Materials of these compositions have not yetbeen exposed to additional processes, such as de-lithiation andlithiation during, respectively, charging and discharging of alithium-ion battery.

Lithium cobalt oxides can be used in cathode active materials forcommercial lithium-ion batteries. These compounds often include lithiumcobalt oxide or derivatives thereof. The performance of such cathodeactive materials can be increased by improving its capacity, workingvoltage, and gravimetric electrode density.

The morphology of particles can also influence the performance ofcathode active materials. Particles can include primary and secondaryparticles. Primary particle and secondary particle size distribution,shape, and porosity can impact the density of lithium cobalt oxideelectrodes. Secondary particles are comprised of agglomerates of thesmaller, primary particles, which are also often referred to as grains.Control of the secondary particle characteristics of shape and densitycan be gained.

The performance of batteries can be improved using compounds andparticles that provide increased capacity, working voltage, andgravimetric electrode density. These and other needs are addressed bythe disclosure herein.

FIG. 1 presents a top-down view of a battery cell 100 in accordance withan embodiment. The battery cell 100 may correspond to a lithium-ion orlithium-polymer battery cell that is used to power a device used in aconsumer, medical, aerospace, defense, and/or transportationapplication. The battery cell 100 includes a stack 102 containing anumber of layers that include a cathode with a cathode active coating, aseparator, and an anode with an anode active coating. More specifically,the stack 102 may include one strip of cathode active material (e.g.,aluminum foil coated with a lithium compound) and one strip of anodeactive material (e.g., copper foil coated with carbon). The stack 102also includes one strip of separator material (e.g., conducting polymerelectrolyte) disposed between the one strip of cathode active materialand the one strip of anode active material. The cathode, anode, andseparator layers may be left flat in a planar configuration or may bewrapped into a wound configuration (e.g., a “jelly roll”).

Battery cells can be enclosed in a flexible pouch. Returning to FIG. 1,during assembly of the battery cell 100, the stack 102 is enclosed in aflexible pouch. The stack 102 may be in a planar or wound configuration,although other configurations are possible. The flexible pouch is formedby folding a flexible sheet along a fold line 112. For example, theflexible sheet may be made of aluminum with a polymer film, such aspolypropylene. After the flexible sheet is folded, the flexible sheetcan be sealed, for example, by applying heat along a side seal 110 andalong a terrace seal 108. The flexible pouch may be less than 120microns thick to improve the packaging efficiency of the battery cell100, the density of battery cell 100, or both.

The stack 102 also includes a set of conductive tabs 106 coupled to thecathode and the anode. The conductive tabs 106 may extend through sealsin the pouch (for example, formed using sealing tape 104) to provideterminals for the battery cell 100. The conductive tabs 106 may then beused to electrically couple the battery cell 100 with one or more otherbattery cells to form a battery pack.

Batteries can be combined in a battery pack in any configuration. Forexample, the battery pack may be formed by coupling the battery cells ina series, parallel, or a series-and-parallel configuration. Such coupledcells may be enclosed in a hard case to complete the battery pack, ormay be embedded within an enclosure of a portable electronic device,such as a laptop computer, tablet computer, mobile phone, personaldigital assistant (PDA), digital camera, and/or portable media player.

FIG. 2 presents a side view of a set of layers for a battery cell (e.g.,the battery cell 100 of FIG. 1) in accordance with the disclosedembodiments. The set of layers may include a cathode current collector202, a cathode active coating 204, a separator 206, an anode activecoating 208, and an anode current collector 210. The cathode currentcollector 202 and the cathode active coating 204 may form a cathode forthe battery cell, and the anode current collector 210 and the anodeactive coating 208 may form an anode for the battery cell. To create thebattery cell, the set of layers may be stacked in a planarconfiguration, or stacked and then wrapped into a wound configuration.

As mentioned above, the cathode current collector 202 may be aluminumfoil, the cathode active coating 204 may be a lithium compound, theanode current collector 210 may be copper foil, the anode active coating208 may be carbon, and the separator 206 may include a conductingpolymer electrolyte.

It will be understood that the cathode active materials described hereincan be used in conjunction with any battery cells or components thereofknown in the art. For example, in addition to wound battery cells, thelayers may be stacked and/or used to form other types of battery cellstructures, such as bi-cell structures. All such battery cell structuresare known in the art.

Surface-modified and structure-stabilized lithium cobalt oxide materialsare disclosed. The materials can be used as cathode active materials inlithium-ion batteries.

In various aspects, the transition-metal oxides are variations oflithium cobalt oxides. In one aspect, the disclosure is directed tocompounds of Formula (I):

Li_(α)MO_(δ)  (I)

wherein M=Co, Mn, Ni, or any combination thereof, 0.95≦α≦2, and 2≦δ≦3.In some variations, 1≦α≦2. In some variations, 1.20≦α. In somevariations, 1.40≦α. In some variations, 1.60≦α. In some variations,1.80≦α. In some variations, α≦1.8. In some variations, α≦1.6. In somevariations, α≦1.4. In some variations, α≦1.2. In some variations, α≦1.8.Further, in some variations, 2.2≦δ. In some variations, 2.4≦δ. In somevariations, 2.6≦δ. In some variations, 2.8≦δ. In some variations, 6<2.8.In some variations, 6<2.6. In some variations, δ≦2.4. In somevariations, δ≦2.2. It will be understood that the boundaries of α and δcan be combined in any variation as above.

In various aspects, the disclosure is directed to compounds of Formula(IIa):

(x)[Li₂M¹O₃].(1−x)[LiM²O₂]  (IIa)

wherein M¹ is one or more cations with an average oxidation state of 4+(i.e., tetravalent), M² is one or more cations with an average oxidationstate of 3+ (i.e., trivalent), and 0≦x≦1. In some variations, M¹ isselected from Ti, Mn, Zr. Mo, Ru, and a combination thereof. In specificvariations, M¹ is Mn. In some variations, M² is selected from B, Na, Mg,Ti, Ca, V, Cr, Mn, Fe, Co, Ni, Cu, Zn, Al, Sc, Y, Ga, Zr, Ru, Mo and acombination thereof. In some variations, M² is selected from Mg, Ca, V,Cr, Mn, Fe, Co, Ni, Cu, Zn, Al, Sc, Y, Ga, Zr, and a combinationthereof.

In specific variations, M² is Co.

It will be appreciated that, in the representation for excess-lithiumtransition-metal oxides, M=[M²]_(1−x)[M¹]_(x), α=1+x, and δ=2+x. In somevariations, α≦1.2. In some variations, α≦1.4. In some variations, α≦1.6.In some variations, α≦1.8. In some variations, 1.2≦α. In somevariations, 1.4≦α. In some variations, 1.6≦α. In some variations, 1.8≦α.It will be understood that the boundaries of x can be combined in anyvariation as above. For the embodiments disclosed herein, cobalt is apredominant transition-metal constituent which allows high voltage, andhigh volumetric energy density for cathode active materials employed inlithium-ion batteries.

In various aspects, the disclosure is directed to compounds of Formula(IIb):

(x)[Li₂M¹O₃].(1−x)[Li_(y)M²O₂]  (IIb)

wherein M¹ is one or more cations with an average oxidation state of 4+(i.e., tetravalent), M² is one or more cations, 0≦x≦1, and 0≦γ≦1. Insome variations, M¹ is selected from Ti, Mn, Zr, Mo, Ru, and acombination thereof. In specific variations, M¹ is Mn. In somevariations, M² is selected from B, Na, Mg, Ti, Ca, V, Cr, Mn, Fe, Co,Ni, Cu, Zn, Al, Sc, Y, Ga, Zr, Ru, Mo and a combination thereof. In somevariations, M² is selected from Mg, Ti, Ca, V, Cr, Mn, Fe, Co, Ni, Cu,Zn, Al, Sc, Y, Ga, Zr, and a combination thereof. In some variations, M²is selected from Mg, Ca, V, Cr, Mn, Fe, Co, Ni, Cu, Zn, Al, Sc, Y, Ga,Zr, and a combination thereof. In specific variations, M² is Co and Mn.

It will be appreciated that, in the representation for excess-lithiumtransition-metal oxides, M=[M²]_(1−x)[M¹]_(x), α=1+x−y+xy, and δ=2+x. Insome variations, α≦0.98. In some variations, α≦1.0. In some variations,α≦1.1. In some variations, α≦1.2. In some variations, 0.95≦α. In somevariations, 1.3≦α. In some variations, 1.6≦α. In some variations, 1.8≦α.It will be understood that the boundaries of a can be combined in anyvariation as above. For the embodiments disclosed herein, cobalt is apredominant transition-metal constituent which allows high voltage, andhigh volumetric energy density for cathode active materials employed inlithium-ion batteries.

In some variations, the disclosure is directed to a compound representedby Formula (III):

Li_(α)Co_(1−x)M_(x)Al_(γ)O_(δ)  (III)

wherein M is B, Na, Mn, Ni, Mg, Ti, Ca, V, Cr, Fe, Cu, Zn, Al, Sc, Y,Ga, Zr, Mo, Ru or a combination thereof or any combination thereof;0.95≦α≦1.10; 0<x<0.50; 0≦γ≦0.05; and 1.95≦δ≦2.60. In some variations, Mis Mn, Ni, or any combination thereof. In some variations, M is Mn, Ni,or a combination thereof, 0.95≦α≦1.10, 0<x<0.50, 0≦γ≦0.05, and1.95≦δ≦2.60. In some variations, 0.01≦γ≦0.03. In some variations,0.001≦γ≦0.005. In some variations, 0.002≦γ≦0.004. In some variations, yis 0.003. In some variations, 0.02≦γ≦0.03. In such variations of Formula(III) where γ≠0 (i.e., aluminum is present), a distribution of aluminumwithin the particle may be uniform or may be biased to be proximate to asurface of the particle. Other distributions of aluminum are possible.In some variations, Al is at least 500 ppm. In some variations, Al is atleast 750 ppm. In some variations, Al is at least 900 ppm. In somevariations, Al is less than or equal to 2000 ppm. In some variations, Alis less than or equal to 1500 ppm. In some variations, Al is less thanor equal to 1250 ppm. In some variations, Al is approximately 1000 ppm.

In additional variations of Formula (III), 1.02≦α≦1.05 and 0.02≦x≦0.05.In further variations of Formula (III), 1.03≦α≦1.05 and x=0.04. It willbe recognized that the components as described above can be in anycombination.

The various compounds of Formulae (I), (IIa), (IIb), and (III) caninclude Mn⁴⁺. Without wishing to be limited to any theory or mode ofaction, incorporating Mn⁴⁺ can improve a stability of oxide under highvoltage charging (e.g., 4.5V) and can also help maintain an R3m crystalstructure (i.e., the α-NaFeO₂ structure) when transitioning through a4.1-4.3V region (i.e., during charging and discharging).

In some embodiments, the disclosure is directed to a powder thatincludes particles. In some aspects, the particles can comprise thecompound of Formula (III) and new formula. In some variations, theparticles comprise a core comprising a compound of Formula (I), Formula(IIa), Formula (IIb) or Formula (III), and a coating disposed over atleast a portion of the core. In further variations, the particlescomprise a core comprising a compound of Formula (III), and a coatingdisposed over at least a portion of the core.

It will be appreciated that the powder may serve as a part or all of acathode active material. The particles described herein can be used in acathode active material in a battery. Such cathode active materials cantolerate voltages equal to or higher than conventional materials (i.e.,relative to a Li/Li⁺ redox couple) without capacity fade. Capacity fadedegrades battery performance and may result from a structuralinstability of the cathode active material, a side reaction withelectrolyte at high voltage, surface instability, a dissolution ofcathode active material into the electrolyte, or some combinationthereof.

In variations in which the particles comprise compounds of Formula (III)and contain aluminum, the aluminum can be referred to as a dopant. Suchaluminum dopants can be distributed uniformly throughout the particle,or alternatively localized along the surface of the particle.

In further variations, the particle comprises a core and a coating. Thecoating can be an oxide material, a fluoride material, or a combinationthereof. In some variations, the coating may be a layer of material incontact with a surface of the core or a reaction layer formed along thesurface of the core. The coating can include an oxide material (e.g.,ZrO₂, Al₂O₃, etc.), a fluoride material (e.g., AlF₃), or a combinationthereof (e.g., AlO_(x)F_(y)). In some embodiments, the oxide materialincludes at least one element selected from the group consisting of Al,Co, Li, Zr, Mg, Ti, Zn, Mn, B, Si, Ga, and Bi. In these embodiments, theoxide material may include oxoanions such as phosphates (e.g., AlPO₄,Co₃(PO₄)₂, LiCoPO₄, etc.). In some embodiments, the fluoride materialincludes at least one element selected from the group consisting of Al,Co, Mn, Ni, Li, Ca, Zr, Mg, Ti, and Na. The coating may include one ormore compositions selected from AlF₃, Al₂O₃, AlPO₄, Co₃(PO₄)₂, LiCoPO₄,and ZrO₂.

The coating can be in any amount known in the art. In some variations,amount of coating may be less than or equal to 7 wt. % of the totalparticle. In some variations, amount of coating may be less than orequal to 5 wt. % of the total particle. In some variations, amount ofcoating may be less than or equal to 0.8 wt. % of the total particle. Insome variations, amount of coating may be less than or equal to 0.6 wt.% of the total particle. In some variations, amount of coating may beless than or equal to 0.4 wt. % of the total particle. In somevariations, amount of coating may be less than or equal to 0.3 wt. % ofthe total particle. In some variations, amount of coating may be lessthan or equal to 0.2 wt. % of the total particle. In some variations,amount of coating may be less than or equal to 0.1 wt. % of the totalparticle. In various aspects, the amount can be chosen such that acapacity of the cathode active material is not negatively impacted.

The coating may include multiple layers of coating material. The coatingmay also be a continuous coating or a discontinuous coating.Non-limiting examples of discontinuous coatings include coatings withvoids or cracks and coatings formed of particles with gaps therebetween.Other types of discontinuous coatings are possible.

Powders comprising the particles described herein can be used as acathode active material in a lithium ion battery. Such cathode activematerials can tolerate voltages equal to or higher than conventionalmaterials (i.e., relative to a Li/Li⁺ redox couple) without capacityfade. Capacity fade degrades battery performance and may result from astructural instability of the cathode active material, a side reactionwith electrolyte at high voltage, surface instability, dissolution ofcathode active material into the electrolyte, or some combinationthereof.

In various aspects, the compounds and/or particles as described herein,when incorporated into a battery as a cathode active material, havelithium ion batteries that can be charged at high voltages withoutcapacity fade. Without wishing to be held to a specific mechanisms ormode of action, the compounds may impede or retard structural deviationsfrom an α-NaFeO₂ crystal structure during charging to at highervoltages.

In various aspects, the compounds as described herein, when incorporatedinto a battery as a cathode active material, have lithium ion batteriesto have voltages greater than 4.2V without capacity fade. In furtheraspects, such batteries have voltages greater than 4.3V. In variousaspects, the lithium cobalt oxide materials are directed to voltagesgreater than 4.4V. In various aspects, the lithium cobalt oxidematerials are directed to voltages greater than 4.5V.

Batteries having cathode active materials that include the disclosedparticles can show improved the battery performance at high voltages.For example, the particles provide for an increased battery capacityover cycles at high voltage (e.g., 4.5V). In certain variation, thedecay rate of the battery is less than 0.7 mAh/g/cycle at a chargepotential of 4.5V. In some variations, the decay rate of the battery isless than 0.6 mAh/g/cycle at a charge potential of 4.5V. In somevariations, the decay rate of the battery is less than 0.5 mAh/g/cycleat a charge potential of 4.5V.

In some additional variations, batteries that include cathode activematerials comprising the disclosed particles lose lower amounts ofenergy per unit mass per cycle. In some embodiments, such batteries loseless than 4 Wh/kg over per cycle when operated at a potential of 4.5V.The disclosure is further directed to methods of making the disclosedcompounds and particles.

In embodiments in which the particle or core comprises compounds ofFormula (VI), Al may be introduced via a surface modification process.For example, and without limitation, the particle may be coated with acoating comprising aluminum and subsequently heated. Thermal energy canenable a reaction between the particle and the coating, thereby infusingaluminum into the core (e.g., doping). In another non-limiting example,the particle may be exposed to a solution that comprises aluminum. Achemical reaction between the particle and the solution can create asurface reaction layer comprising aluminum. The particle may besubsequently heated (e.g., to diffuse aluminum from the surface reactionlayer into the particle, convert the surface reaction layer into acoating, etc.). In a further non-limiting example, the particle may becontacted with particles that comprise aluminum, such as during milling.Mechanical energy creates compressive forces, shear forces, or acombination thereof, to fuse the aluminum particles to the particle(e.g., bond Al₂O₃ nanoparticles to the particle). These surfacemodification processes can allow the core to achieve an aluminum contentbetween 0<γ≦0.03. Other surface modification processes are possible.

In various embodiments, the performance of batteries including thecompounds and/or powders can increase battery capacity and/or reduce theloss of available power in a fully charged battery over time.

The disclosure is further directed to methods of modifying a surface ofparticles by wet processing or dry processing.

In one aspect, the disclosure is directed to methods of makingparticles. A precursor solution comprising a first amount of a precursordissolved in a solvent is prepared. The powders comprises a compoundaccording to Formula (I), (IIa), (IIb) or (III). The precursor solutionis added to the powder to form a wet-impregnated powder. Thewet-impregnated powder is heated to an elevated temperature.

In another aspect, the first precursor is dissolved in a first portionof the solvent to form a first solution. The first solution is added tothe powder to form a partial wet-impregnated powder.

A second precursor is dissolved into a second portion of solvent to forma second solution. The second is added to the partial wet-impregnatedpowder to produce a wet-impregnated powder. The wet-impregnated powderis then heated at an elevated temperature.

Wet-impregnation involves adding solvent to particles of the powderuntil the particles exhibit a damp consistency (e.g., paste-like). Invarious aspects, the amount of solvent can be selected such that, whenthe precursor solution is added to the powder, the wet-impregnatedpowder so-produced exhibits a damp consistency. The method additionallyincludes heating the wet-impregnated powder at an elevated temperature.It will be appreciated that the amount of solvent may be determined byselecting a known amount of the powder and progressively adding solventuntil all particles of the powder appear wet, but do not flow (i.e.,show a damp consistency). A ratio of solvent to powder (e.g., grams ofsolvent per grams of the powder) may be scaled as needed to accommodatedifferent amounts of the powder when utilizing the method. Aconcentration of the at least one precursor may then be selected toapply a desired quantity of material onto the surface of the particles.Representative variations of the method are described in relation toExamples 1, 3, 4, 5, and 6.

In some embodiments, heating the wet-impregnated powder includes dryingthe wet-impregnated powder. In some embodiments, the at least oneprecursor includes aluminum (e.g., see Example 1).

In some embodiments, preparing the precursor solution includesdissolving a first precursor into a first portion of solvent to form afirst solution and dissolving a second precursor into a second portionof solvent to form a second solution. The first portion of solvent andthe second portion of solvent, in total, may correspond to the amount ofsolvent. In these embodiments, preparing the precursor solution alsoincludes mixing the first solution with the second solution, therebyforming the precursor solution. In some instances, the first precursorincludes aluminum and the second precursor includes phosphate (e.g., seeExample 3). In other instances, the first precursor includes cobalt andthe second precursor includes phosphate (e.g., see Example 4). In stillother instances, the first precursor include aluminum and the secondprecursor includes lithium (e.g., see Example 5).

In some embodiments, preparing the precursor solution includesdissolving the first precursor into the first portion of solvent to formthe first solution, dissolving the second precursor into the secondportion of solvent to form the second solution, and dissolving a thirdprecursor into a third portion of solvent to form the third solution.The first portion of solvent, the second portion of solvent, and thethird portion of solvent, in total, correspond to the amount of solvent.In such embodiments, preparing the precursor solution also includesmixing the first solution, the second solution, and the third solutionthereby forming the precursor solution.

In some embodiments, at least one of the first precursor, the secondprecursor, and the third precursor include lithium. In some embodiments,the first precursor includes cobalt, the second precursor includeslithium, and the third precursor includes phosphate (e.g., see Example6).

In some embodiments, adding the first solution to the powder includesdrying the partial wet-impregnated powder. In some embodiments, heatingthe wet-impregnated powder includes drying the wet-impregnated powder.In some embodiments, the first precursor includes aluminum and thesecond precursor include fluorine (e.g., see Example 2).

According to an illustrative embodiment, a method for modifying asurface of particles includes stirring a suspension of particles. Theparticles include the compound of Formula (III).

The method also involves adding one or more precursor to the suspensionof particles while stirring. In some embodiments, the methodadditionally includes filtering the particles after adding the precursorsolution. Representative variations of the method are described inrelation to Examples 7-9.

In some embodiments, the method includes filtering the particles afteradding the at least one precursor and heating the filtered particles toan elevated temperature. In some embodiments, the precursor solution caninclude aluminum or cobalt (e.g., see Example 8). Non-limiting examplesof the metal precursor include an aluminum precursor, e.g., Al(NO₃)₃,and a cobalt precursor, e.g., Co(NO₃)₃.

According to an illustrative embodiment, a method for modifying asurface of particles in a powder includes blending particles ofnanocrystalline material with particles of the powder. The particles ofthe powder can include a compound according to Formula (I), (IIa), or(III), as described herein. The particles can be combined with thenanocrystalline material and while blending, and/or subjected tocompressive forces, shear forces, or a combination thereof. Such forcescan induce the nanocrystalline material particles to bond to surfaces ofthe particles of the powder. The nanocrystalline material particles andthe powder particles can be blended in such a ratio that thenanocrystalline material particles form a predetermined amount ofcoating on the powder particles. Representative variations of the methodare described in relation to Examples 10-12. In some embodiments, thenanocrystalline material particles can include an aluminum oxidematerial, an aluminum fluoride material, or a combination thereof.

In some variations, the disclosure is directed to a compound representedby Formula (IV):

Li_(α)Co_(1−x)Mn_(x)O_(δ)  (IV)

wherein 0.95≦α≦1.10, 0≦x≦0.10, and 1.90≦δ≦2.20. In some variations,0.98≦α≦1.01. In some variations of Formula (IV), 0.98≦α≦1.01 and x=0.03.In some variations of Formula (IV), 1.00≦α≦1.05. In some variations,0<x≦0.10. In a further variations, the disclosure is directed to acompound represented by Formula (IV), wherein 0.95≦α≦1.05 and0.02≦x≦0.05. In a further aspect, the disclosure is directed to acompound represented by Formula (IV), wherein 0.95≦α≦1.05 and x=0.04. Insome variations, x=0.03. In further variations of Formula (IV),1.01≦α≦1.05 and 0.02≦x≦0.05. In still further variations of Formula(IV), 1.01≦α≦1.05 and x=0.04. In some variations of Formula (IV),1.00≦α≦1.10. In other variations of Formula (IV), 1.00≦α≦1.05. In afurther aspect, the disclosure is directed to a compound represented byFormula (IV), wherein 0.98≦α≦1.01, x=0.03, and δ=2.

It will be appreciated that are presents a molar ratio of lithiumcontent to total transition-metal content (i.e., total content of Co andMn). In various aspects, increasing lithium content can increasecapacity, improve stability, increase gravimetric density of particlescomprising the compound, increase particle density, and/or increaseparticle strength of the cathode active material. In various aspects,decreasing lithium content can increase capacity, improve stability,increase gravimetric density of particles comprising the compound,increase particle density, and/or increase particle strength of thecathode active material.

In some variations, the compound of Formula (IV) may be represented as asolid solution of two phases, i.e., a solid solution of Li₂MnO₃ andLiCoO₂. In these variations, the compound may be described according toFormula (Va):

(x)[Li₂MnO₃].(1−x)[LiCoO₂]  (Va)

where Mn is a cation with an average oxidation state of 4+ (i.e.,tetravalent) and Co is a cation with an average oxidation state of 3+(i.e., trivalent). A more compact notation for Formula (Va) is givenbelow:

Li_(1+x)Co_(1−x)Mn_(x)O_(2+x)  (VI)

In Formula (VI), x describes including both Mn and Co. Due to differingvalences between Mn and Co, such inclusion of Mn may influence lithiumcontent and oxygen content of the compound.

In Formula (IV), the composition of ‘x’ can be 0≦x≦0.10. In somevariations, 0<x≦0.10. In such variations, the lithium content can befrom 1 to 1.10 in Formula (VI), and the oxygen content can be from 2 to2.10. However, the compounds disclosed herein have lithium contents andoxygen contents that may vary independently of x. For example, andwithout limitation, the lithium and oxygen contents may vary fromstoichiometric values due to synthesis conditions deliberately selectedby those skilled in the art. As such, subscripts in Formulas (V) and(VI) are not intended as limiting on Formula (IV), i.e., α is notnecessarily equal to 1+x, and δ is not necessarily equal 2+x. It will beappreciated that the lithium content and the oxygen content of compoundsrepresented by Formula (IV) can be under-stoichiometric orover-stoichiometric relative to the stoichiometric values of Formula(VI).

In some variations, the compound of Formula (IV) may be represented as asolid solution of two phases, i.e., a solid solution of Li₂MnO₃ andLiCoO₂. In these variations, the compound may be described according toFormula (Vb):

(x)[Li₂MnO₃].(1−x)[Li_((1−y))Co_((1−y))Mn_(y)O₂]  (Vb)

where Mn is a cation with an average oxidation state of 4+ (i.e.,tetravalent) and Co is a cation with an average oxidation state of 3+(i.e., trivalent).

The disclosure is further directed to powders comprising compoundsdescribed herein. In various aspects, the disclosure is directed to apowder that includes particles comprising Li_(α)Co_(1−x)Mn_(x)O_(δ)where 0.95≦α≦1.10, 0≦x≦0.10, and 1.90≦δ≦2.20. In some variations,0≦y≦0.10. The powder may serve as part or all of a cathode activematerial (i.e., the cathode active material includes the powder). Insome embodiments, 0.98≦α≦1.01 and x=0.03. In some embodiments,1.00≦α≦1.05. In further embodiments, 1.01≦α≦1.05 and 0.02≦x≦0.05. Instill further embodiments, 1.01≦α≦1.05 and x=0.04. In some embodiments,1.00<α≦1.10. In other embodiments, 1.00<α≦1.05.

In some variations, the compound of Formula (IV) may be represented as asolid solution of two phases, i.e., a solid solution of Li₂MnO₃ andLiCoO₂. In these variations, the compound may be described according toFormula (Va) or Formula (Vb), where Mn is a cation with an averageoxidation state of 4+ (i.e., tetravalent) and Co is a cation with anaverage oxidation state of 3+ (i.e., trivalent).

Alternatively, a more compact notation is depicted as Formula (Vc):

Li_(1+x−y−xy)Co_((1−x)*(1−y))Mn_((x+y−x*y))O_(2+x)  (Vc)

In Formula (Vc), x can describe both Mn and Co. Without wishing to beheld to a particular mechanism or mode of action, because of differingvalences between Mn and Co, inclusion of Mn may influence lithiumcontent and oxygen content of the compound.

In Formula (Vc), the combination of ‘x’ and ‘y’ at least zero and lessthan or equal to 0.10. In some variations, the combination of ‘x’ and‘y’ can be greater than zero and less than or equal to 0.10. In suchvariations, the lithium content can be any range described herein forother Formulae. In some variations, Li can be from 0.9 to 1.10. In somevariations, oxygen content can be from 2 to 2.10. It will be recognizedthat, as with all Formulae presented herein, that the compoundsdisclosed herein have lithium contents and oxygen contents that may varyindependently of x and y.

The compounds and powders can be in a cathode active material forlithium ion batteries, as described herein. These cathode activematerials assist energy storage by releasing and storing lithium ionsduring, respectively, charging and discharging of a lithium-ion battery.

Without wishing to be limited to a specific mechanism or mode of action,the characteristics of the powder can provide improved batteryperformance when the powder is used as a cathode active material.Powders comprising the compounds described herein have increased tapdensities over previously known compounds. Batteries comprising thesepowders as a cathode active material have an increased volumetric energydensity.

In some instances, batteries having such cathode active materials have aspecific capacity greater than 130 mAh/g. In some instances, thespecific capacity is greater than 140 mAh/g. In some instances, thespecific capacity is greater than 150 mAh/g. In some instances, thespecific capacity is greater than 160 mAh/g. In some instances, thespecific capacity is greater than 170 mAh/g.

Increasing an initial lithium content in the cathode active materials(e.g., an as-prepared lithium content) can increase the volumetricenergy density and/or cycle life.

The cathode active material can exhibit a high tap density and/orimproved particle strength. In some instances, the cathode activematerial can exhibit a tap density equal to or greater than 2.1 g/cm³.In some instances, the cathode active material can exhibit a tap densityequal to or greater than 2.2 g/cm³. In some instances, the cathodeactive material can exhibit a tap density equal to or greater than 2.3g/cm³. In some instances, the cathode active material can exhibit a tapdensity greater than or equal to 2.4 g/cm³.

In some variations, the disclosure is directed to a cathode activematerial for lithium-ion batteries that includes a lithium cobalt oxidehaving a tetravalent metal of Mn⁴⁺. In these materials, the trivalent Coion, Co³⁺, can serve as host to supply the capacity. Without wishing tobe limited to any theory or mode of action, incorporating Mn⁴⁺ canimprove a stability of lithium cobalt oxide under high voltage chargingand can also help maintain an R3m crystal structure when transitioningthrough a 4.1-4.6 V region (i.e., during charging and discharging).

In some instances, the voltage charge can be equal to or greater than4.4 V. In some instances, the voltage charge can be equal to or greaterthan 4.5 V. In some instances, the voltage charge can be equal to orgreater than 4.6 V.

A degree of Mn can influence an amount of additional lithium desired forthe cathode active material. For example, and without limitation, acomposition of lithium cobalt oxide having 92% Co and 8% Mn maycorrespond to a lithium content of 6 to 10 mole percent in excess ofunity. In general, however, ranges for the lithium content may varybased on the degree of manganese substitution, and as shown in relationto FIG. 13, may be determined by those skilled in the art usingempirical data.

FIG. 13 presents a plot of data representing an influence of molar ratioon a capacity (i.e., a first-cycle discharge capacity) and efficiency ofa cathode active material comprising Li_(α)Co_(0.96)Mn_(0.04)O_(δ)(i.e., x=0.04), according to an illustrative embodiment. The molarratio, indicated on the abscissa, corresponds to a, the molar ratio oflithium content to total transition-metal content (i.e., described asthe “Li/TM ratio” in FIG. 13). To determine the molar ratio, the cathodeactive material was characterized chemically using inductively-coupledplasma optical emission spectroscopy (ICP-OES), as known to thoseskilled in the art. The capacity and efficiency are indicated,respectively, on the left-side and right-side ordinates.

With further reference to FIG. 13, a first curve 300 representing achange in capacity with the molar ratio is fitted to a first set of datapoints 302. A second curve 304 representing a change in efficiency withthe molar ratio is fitted to a second set of data points 306. For thisparticular composition (i.e., x=0.04), the first curve 300 exhibits amaximum in a range corresponding to 0.98≦α≦1.05. However, it will beappreciated that limits of the range may change in response to changesin x, which represents an amount of Mn in the cathode material. Ingeneral, those skilled in the art may alter a and x to achieve a desiredcombination of capacity and efficiency.

In certain variations, the compounds described herein can allow forexcess lithium storage. In FIG. 13, increasing lithium (i.e.,0.98<α≦1.05) is demonstrated to increase the capacity of the cathodematerial relative to unity (i.e., α=1.00). This increased capacityallows those skilled in the art to match a particular (increased)capacity to a desired efficiency. Such increased capacity is unexpected.In various aspects, additional lithium can normally expected to functionas a contaminant in the cathode material, degrading its performance.Indeed, when the excess of lithium exceeds a threshold value (e.g.,exceeds α˜1.05 in FIG. 13), both capacity and efficiency decrease.

In various aspects, the compounds described herein provide for increasedcapacity and stability of the cathode active material over knowncompounds. FIG. 14 presents a plot of data representing an influence ofthe molar ratio, represented by α, and Mn content, represented by x, ona c-axis lattice parameter of the compound of Formula (IV), i.e.,Li_(α)Co_(0.96)Mn_(0.04)O_(δ), according to an illustrative embodiment.Oxygen in the composition may correspond to δ=2, although variationsfrom this stoichiometry are possible (i.e., within 1.90≦δ≦2.20). Thedata are generated using techniques of X-ray diffraction, as known bythose skilled in the art. The (003) peak in the R3m diffraction patternfor LiCoO₂ characteristically shifts according x and α. For a given x(e.g., 0.04 or 4 mole percent), the c-lattice contracts with increasingα (i.e., as α increases from 1.0062 to 1.0925). Without wishing to belimited to any theory or mode of action, it is believed that excess Limoves into a transition metal layer of Li_(α)Co_(0.96)Mn_(0.04)O_(δ) dueto the presence of Mn⁴⁺. This displacement increases the lithiumcapacity and stability of the material.

FIG. 15 presents a plot of data representing a change in the c-axislattice parameter with molar ratio for Li_(α)Co_(0.96)Mn_(0.04)O_(δ),according to an illustrative embodiment. (The molar ratio, α, isindicated on the abscissa as “ICP Li/TM”). Oxygen in the composition maycorrespond to δ=2, although variations from this stoichiometry arepossible (i.e., within 1.90≦δ≦2.20). To determine a, the cathode activematerial was characterized chemically using ICP-OES, as known to thoseskilled in the art. The change in the c-axis lattice parameter follows asigmoidal curve. The sigmoidal curve tends to become asymptotic atextremes of α (i.e., the lowest and highest values of a shown in FIG.15).

The disclosure is further directed to methods of producing a powdercomprising Li_(α)Co_(1−x)Mn_(x)O_(δ). The method includes the steps ofmixing a lithium source with precursor particles to produce a reactant,and then heating the reactant to a high temperature.

Precursors of the lithium-ion cathode materials can be calcined toobtain the positive electrode material. However, it can be difficult tocontrol the particle sintering process to produce high density particlesand at the same time produce a high capacity material. State of the artprocedures add a variable amount of extra lithium of up to 10 wt % dueto its high evaporation rate at high temperatures.

The precursor particles comprise a transition-metal hydroxide comprisingCo and Mn. Non-limiting examples of the lithium source include lithiumhydroxide (i.e., LiOH) and lithium carbonate (i.e., Li₂CO₃). However,other lithium sources are possible.

The method also includes heating the reactant to a temperature equal toor greater than 800° C. In these methods, 0≦x≦0.10 and 1.90≦δ≦2.20. Insome variations, 0<x≦0.10. The ratio of the lithium source to theprecursor particles is selected such that 0.95≦α≦1.10. This ratio may beequal to or greater than the molar ratio, α, due to evaporative lossesof lithium during heating. In some embodiments, the temperature isbetween 800-1200° C.

In some aspects, the temperature of heating is from about 800 to about1000° C. In other aspects, the temperature of heating is from about 1000to about 1100° C. In other aspects, the temperature of heating is fromabout 1100 to about 1200° C. In still other aspects, the temperature ofheating is from about 900 to about 1000° C. In still yet other aspects,the temperature of heating is from about 800 to about 900° C. Withoutwishing to be limited to any mechanism or mode of action, temperaturesin the aforementioned ranges allow particles of powder to exhibitgravimetric density and strength sufficient for lithium-ion batteryapplications. These ranges also correspond to improved capacities andfirst-cycle efficiencies. Again, without wishing to be limited to anymechanism or mode of action, it will be appreciated that highgravimetric densities allow increased energy densities for the cathodeactive material. Particle strength can improve efficient handling duringbattery manufacturing and for cycle stability during battery operation.

In various aspects, the molar ratio (i.e., α), the temperature, andcorresponding heating periods can control particle sintering anddensification. FIG. 16 presents a series of scanning electronmicrographs of powder prepared at 900° C., 1000° C., 1050° C., and 1100°C., according to an illustrative embodiment. The temperature increasesfrom left to right and a magnification increases from top to bottom. Acomposition of the powder particles corresponds to α=1.04 and x=0.04. At900° C. and 1000° C., particles of the powder retain a plate-likestructure of the precursor particles. The powder exhibits a tap densityof 2.0 and 2.1 g/cm³, respectively. At 1050° C. and 1100° C., however, amorphology of individual particles in the powder has changed to smooth(i.e., a smooth surface). This smooth morphology suggests a partialmelting during. The corresponding tap density increases to 2.3-2.4g/cm³. These powders show greater strength because the grains (i.e., theprimary particles) have grown and are better bonded together.

Moreover, the grains have decreased in number and fewer grain boundariesare present therein.

In these methods, additional lithium content controls a degree ofsintering of the precursor particles. Such additional lithium contentalso controls a capacity of the powder, when included as a cathodeactive material. It will be understood that sufficient lithium should bepresent to react with and sinter the precursor particles, but not riskover-sintering the precursor particles. Over-sintering can produce asolid mass. Even if a solid mass can be avoided, excessive lithium maylower capacity and efficiency of the cathode active material.

The particle density and strength increases with increasing molar ratio(i.e., α). FIG. 17 presents a series of scanning electron micrographsshowing an influence of temperature and molar ratio (α) on particlemorphology, according to an illustrative embodiment. A composition ofthe powder (i.e., particles therein) corresponds to x=0.04 with aincreasing progressively from 1.00, to 1.04, to 1.06, to 1.08, and to1.10 (i.e., from left to right in FIG. 17). Two temperatures arepresented, i.e., 1050° C. and 1100° C. Oxygen in the composition maycorrespond to δ=2, although variations from this stoichiometry arepossible (i.e., within 1.90≦δ≦2.20).

The heating temperature can have an effect on the surface morphology andincreased tap density of the powder. In the embodiment depicted in FIG.17, at 1050° C. and a values less than 1.02 the secondary particles arefree-flowing after calcination. However, primary grains are not wellbonded for strength. At higher molar ratios, however, individual grainsfused together better.

At 1100° C., the secondary particles had smooth surfaces and well-bondedgrains. As the molar ratio is increased (i.e., at 1100° C.), thesecondary particles begin to bond together, forming a rigid sinteredmass of particles. This rigid sintered mass may be broken apart bygrinding.

In some embodiments, 1.00≦α≦1.05. In other embodiments of the method,1.00<α≦1.10. In further embodiments, 1.00≦α≦1.05.

In some embodiments, 1.01≦α≦1.05 and 0.02≦x≦0.05. In furtherembodiments, 1.01≦α≦1.05 and x=0.04.

FIG. 18 presents a plot of data representing an influence of mixingratio on a capacity and an efficiency of a cathode active materialcomprising Li_(α)Co_(0.96)Mn_(0.04)O_(δ), according to an illustrativeembodiment. The mixing ratio corresponds to the ratio of lithium sourcemixed the precursor particles. The cathode active material includes thepowder depicted in FIG. 17 and calcined at 1050° C. Oxygen in thecomposition may correspond to 8=2 although variations from thisstoichiometry are possible (i.e., within 1.90≦δ≦2.20).

In FIG. 18, the abscissa shows an increase of the mixing ratio from 1.00to 1.10. The cathode active material has a maximum discharge capacity of192 mAh/g (i.e., during discharge from 4.5 V to 2.75 V) at a mixingratio of 1.04, which corresponds to α=1.01 as measured by ICP-OES. Highdischarge values of ˜190 mAh/g for mixing ratios of 1.06, 1.08, and 1.10(i.e., α=1.02, 1.03, and 1.04, respectively by ICP-OES) can also beobtained.

In some variations, the disclosure is directed to a compound representedby Formula (VII):

Li_(α)Co_(1−x−y)M_(y)Mn_(x)O_(δ)  (VII)

wherein 0.95≦α≦1.30, 0<x≦0.30, 0≦y≦0.10, and 1.98≦δ≦2.04, and M is atleast one element selected from the group consisting of B, Na, Mg, Ti,Ca, V, Cr, Fe, Co, Ni, Cu, Zn, Al, Sc, Y, Ga, Zr, Ru, and Mo. Thecompound of Formula (VII) is single phase. The compound can have atrigonal R3m crystal structure. In further variations, 0.98≦α≦1.16 and0<x≦0.16. In some variations 0.98≦α≦1.16, 0<x≦0.16, 0<y≦0.05,1.98≦δ≦2.04.

In some variations, the disclosure is directed to a compound representedby Formula (VIII):

Li_(α)Co_(1−x−y)Al_(y)Mn_(x)O_(δ)  (VIII)

wherein 0.95≦α≦1.30, 0≦x≦0.30, 0≦y≦0.10, and 1.98≦δ≦2.04. In somevariations, 0.96≦α≦1.04, 0<x≦0.10, 0≦y≦0.10, and 1.98≦δ≦2.04. In somevariations, the compounds represented by Formula (VIII) have0.98≦α≦1.01, 0.02≦x≦0.04, 0≦y≦0.03, and 1.98≦δ≦2.04. The compound ofFormula (VIII) is a single phase. The compound can have trigonal R3mcrystal structure.

In some instances, the compounds represented by Formulas (VII) and(VIII) have α>1+x. In other instances, α<1+x. As such, α in Formulas(VII) and (VIII) can deviate from α=1+x, which may be associated with asolid-solution between Li₂MnO₃ and (1−x)LiCo_(1−y)M_(y)O₂. This solidsolution can be represented by xLi₂MnO₃.(1−x)LiCo_(1−y)M_(y)O₂, andxLi₂MnO₃.(1−x)Li1−yCo_(1−y)M_(y)O₂, or in compact notation,Li_(1−x)Co_(1−x−y+xy)M_((1−x))*_(y)Mn_(x)O_(2+x) orLi_(1+x−y+xy)Co_(1−x−y+xy)M_((1−x)*y)Mn_(x)O_(2+x)

As described, the various compounds do not include a second phase, suchas a second phase having a different crystal structure. It will beappreciated that Li₂MnO₃ is a “rock salt” phase having a monoclinic C2/mcrystal structure. Thus, cathode active materials based on the solidsolution between Li₂MnO₃ and LiCo_(1−y)M_(y)O₂ have portions of “rocksalt” phase that exhibit the monoclinic C2/m crystal structure. This“rock salt” phase occurs in addition to any phases associated withLiCo_(1−y)M_(y)O₂, making the solid solution bi-phasic (ormulti-phasic). In contrast, the cathode active materials represented byFormulas (VII) & (VIII), and variations thereof, are single phase andhave only a trigonal R3m crystal structure.

Without wishing to be held to any particular mechanism or mode ofaction, manganese is incorporated into the compounds of Formulas (VII)and (VIII) to stabilize its R3m crystal structure, although otherconstituents of M may also contribute to stabilization. The compoundsinclude a sub-lattice of Co in their R3m crystal structures in which Mnis uniformly distributed. Alternatively, in some variations, clusters ofmanganese (e.g., pairs, triplets, etc.) occur in the sub-lattice of Cothat are uniformly distributed therein. Clustering can be detected, forexample, by nuclear magnetic resonance (NMR) as described herein. Thepresence of Mn in the compounds may limit phase transitions from the R3mcrystal structure during battery operation (e.g., charging, discharging,etc.). The presence of Mn may also improve an oxidative stability of thecompound at higher voltages (e.g., voltages equal to or greater than4.0V).

In some variations, x corresponds to a degree that Mn substitutes forCo. The degree of Mn substitution can correlate to the stability ofcompounds when used in cathode active materials. In various aspects, thesubstitution of Mn for Co can be greater than or equal to a lowersubstitution limit. Alternatively, the substitution of Mn for Co can beequal to or less than a substitution limit.

In some variations, x is at least 0.001. In some variations, x is atleast 0.01. In some variations, x is at least 0.02. In some variations,x is at least 0.03. In some variations, x is at least 0.04. In somevariations, x is at least 0.05. In some variations, x is at least 0.06.In some variations, x is at least 0.07. In some variations, x is atleast 0.08. In some variations, x is at least 0.09. In some variations,x is at least 0.10. In some variations, x is at least 0.12. In somevariations, x is at least 0.14. In some variations, x is at least 0.16.In some variations, x is at least 0.18. In some variations, x is atleast 0.20. In some variations, x is at least 0.22. In some variations,x is at least 0.24. In some variations, x is at least 0.26. In somevariations, x is at least 0.28.

In some variations, x is less than or equal to an upper substitutionlimit. In some variations, x is less than or equal to 0.30. In somevariations, x is less than or equal to 0.28. In some variations, x isless than or equal to 0.26. In some variations, x is less than or equalto 0.24. In some variations, x is less than or equal to 0.22. In somevariations, x is less than or equal to 0.20. In some variations, x isless than or equal to 0.18. In some variations, x is less than or equalto 0.16. In some variations, x is less than or equal to 0.14. In somevariations, x is less than or equal to 0.12. In some variations, x isless than or equal to 0.10. In some variations, x is less than or equalto 0.09. In some variations, x is less than or equal to 0.08. In somevariations, x is less than or equal to 0.07. In some variations, x isless than or equal to 0.06. In some variations, x is less than or equalto 0.05. In some variations, x is less than or equal to 0.04. In somevariations, x is less than or equal to 0.03.

It will be understood that the lower and upper substitution limits maybe combined in any variation as above to define a range for x, in anycombination. For example, and without limitation, x may range from 0.001to 0.01. x may range from 0.02 to 0.05 (i.e., 0.02≦x≦0.07). In anothernon-limiting example, x may range from 0.24 to 0.28 (i.e., 0.06≦x≦0.10).In still yet another non-limiting example, x may range from 0.24 to 0.28(i.e., 0.22≦x≦0.28). Other combinations of the upper and lower limitsare possible.

Furthermore, without wishing to be held to any particular mechanism ormode of action, a content of lithium may be selected in the compounds ofFormulas (VII) and (VIII) to stabilize its R3m crystal structure andimprove battery performance. The content of lithium may selectivelycomplement a degree of substitution for Co (i.e., via Mn, M, or Alsubstitutions). For example, and without limitation, α may be selectedto be about 1+x. Relative to α-=1, this selection may improve stabilityof the R3m crystal structure during lithiation and de-lithiation (seeFIG. 29). In another non-limiting example, α may be selected to begreater than 1+x to accommodate substitutes in addition to Mn (i.e., Mand y). These substitutes may allow the compounds to have improveddischarge energies (see FIG. 33). In still yet another example, thelithium content may be selected according to α<1+x to enhance batteryperformance. As shown by FIG. 30, Li_(1.003)Co_(0.97)Mn_(0.03)O₂maintains higher discharge energy after repeated cycling thanLi_(1.014)Co_(0.97)Mn_(0.03)O₂, even though the latter has a highervalue for a. In some variations, 0.98≦Li/Me≦1.01

It will be appreciated that a corresponds to a ratio of Li to Co and itssubstitutes (i.e., with reference to Formula (VII), M and Mn, and withreference to Formula (VIII), M, Mn, and Al). With respect to Formula(VII), the ratio can be depicted as [Li]/[Co_(1−x−y)M_(y)Mn_(x)]. Withrespect to Formula (VII), the ratio can be depicted as[Li]/[Co_(1−x−y)Al_(y)Mn_(x)]. For compounds with y=0, α corresponds toa ratio of Li to Co and Mn, i.e., [Li]/[Co_(1−x)Mn_(x)]. This latterratio can be referred as the lithium to transition metal ratio (i.e.,Li/TM).

In some variations, the compounds remain single phase and have thetrigonal R3m crystal structure. In some variations, α can be equal togreater than a lower limit. In some variations, α is at least 0.95. Insome variations, α is at least 0.98. In some variations, α is at least1.00. In some variations, α is greater than 1.00. In some variations, αis at least 1.02. In some variations, α is at least 1.04. In somevariations, α is at least 1.06. In some variations, α is at least 1.08.In some variations, α is at least 1.10. In some variations, α is atleast 1.12. In some variations, α is at least 1.14. In some variations,α is at least 1.16. In some variations, α is at least 1.20. In somevariations, α is at least 1.22. In some variations, α is at least 1.24.In some variations, α is at least 1.26. In some variations, α is atleast 1.28.

Similarly, α can be less than or equal to a lower limit. In somevariations, α is less than or equal to 1.30. In some variations, α isless than or equal to 1.28. In some variations, α is less than or equalto 1.26. In some variations, α is less than or equal to 1.24. In somevariations, α is less than or equal to 1.22. In some variations, α isless than or equal to 1.20. In some variations, α is less than or equalto 1.16. In some variations, α is less than or equal to 1.14. In somevariations, α is less than or equal to, 1.12. In some variations, α isless than or equal to 1.10. In some variations, α is less than or equalto 1.08. In some variations, α is less than or equal to 1.06. In somevariations, α is less than or equal to 1.04. In some variations, α isless than or equal to 1.02. In some variations, α is less than or equalto 1.00. In some variations, α is less than 1.00. In some variations, αis less than or equal to 0.98. In these variations, the compounds alsoremain single phase and have the trigonal R3m crystal structure.

It will be understood that the lower and upper limits of α may becombined in any variation as above to define a range. For example, andwithout limitation, α may range from 0.95 to 1.00 (i.e., 0.95≦α≦1.00).In another non-limiting example, α may range from 1.00 to 1.06 (i.e.,1.00≦α≦1.08). In still yet another non-limiting example, α may rangefrom 1.22 to 1.28 (i.e., 1.22≦α≦1.28). Other combinations of the upperand lower limits are possible.

It will also be understood that the lower and upper specification limitsfor x and the lower and upper limits for α may be combined in anyvariation as above to define combinations of ranges for x and α. Forexample, and without limitation, x≧0.03 and 0.98≦α≦1.10. In anothernon-limiting example, 0.02≦x≦0.10 and 0.95≦α≦1.12. In still yet anothernon-limiting example, 0.04≦x≦0.12 and 0.95≦α≦1.16. Other combinations ofranges are possible.

In some variations, α approaches 1+x. In these variations, α mayapproach 1+x within a tolerance not greater than 5%. The tolerance maycorrespond to (1−t)*(1+x)≦α≦(1+x)*(1+t) where t≦0.05. In somevariations, the tolerance is less than or equal to ±5.0%. In someinstances, the tolerance is less than or equal to ±4.5%. In someinstances, the tolerance is less than or equal to ±4.0%. In someinstances, the tolerance is less than or equal to ±3.5%. In someinstances, the tolerance is less than or equal to ±3.0%. In someinstances, the tolerance is less than or equal to ±2.5%. In someinstances, the tolerance is less than or equal to ±2.0%. In someinstances, the tolerance is less than or equal to ±1.5%. In someinstances, the tolerance is less than or equal to ±1.0%.

In some instances, the tolerance is at least ±1.0%. In some instances,the tolerance is at least ±0.5%. In some instances, the tolerance is atleast ±1.0%. In some instances, the tolerance is at least ±1.5%. %. Insome instances, the tolerance is at least ±2.0%. In some instances, thetolerance is at least ±2.5%. In some variations, the tolerance is atleast ±3.0%. In some instances, the tolerance is at least ±3.5%. In someinstances, the tolerance is at least ±4.0%. In some instances, thetolerance is at least ±4.5%.

It will be understood that, when a approaches 1+x, the correspondingcompounds maintain a single-phase character and do not have inclusionsof Li₂MnO₃ therein. Moreover, the compounds can exhibit an improvedresistance to phase transitions during charging and discharging, as wellas improved discharge energies. Non-limiting examples of such compoundsinclude Li_(0.050)Co_(0.96)Mn_(0.04)O₂, Li_(1.074)Co_(0.96)Mn_(0.04)O₂,Li_(1.197)Co_(0.78)Mn_(0.22)O₂, and Li_(1.247)Co_(0.72)Mn_(0.28)O₂.

In some variations, the compound is selected from amongLi_(1.050)Co_(0.96)Mn_(0.04)O₂, Li_(1.074)Co_(0.96)Mn_(0.04)O₂,Li_(1.081)Co_(0.96)Mn_(0.04)O₂, Li_(1.089)Co_(0.96)Mn_(0.04)O₂,Li_(1.050)Co_(0.96)Mn_(0.07)O₂, Li_(1.065)Co_(0.90)Mn_(0.10)O₂,Li_(1.100)Co_(0.90)Mn_(0.10)O₂, Li_(1.110)Co_(0.90)Mn_(0.07)O₂,Li_(1.050)Co_(0.90)Mn_(0.10)O₂, Li_(0.975)Co_(0.84)Mn_(0.16)O₂,Li_(1.050)Co_(0.84)Mn_(0.16)O₂, Li_(1.114)Co_(0.84)Mn_(0.16)O₂,Li_(1.197)Co_(0.78)Mn_(0.22)O₂, Li_(1.190)Co_(0.72)Mn_(0.28)O₂, andLi_(1.247)Co_(0.72)Mn_(0.28)O₂. In these compounds, manganesesubstitutes for cobalt without inducing the formation of Li₂MnO₃, i.e.,the compounds are single phase and have the trigonal R3m crystalstructure.

In some variations, the compound is Li_(0.991)Mn_(0.03)Co_(0.97)O₂. Insome variations, the compound is Li_(0.985)Mn_(0.03)Co_(0.97)O₂.

The disclosure is further directed to powders comprising compoundsdescribed herein. In various aspects, the disclosure is directed to apowder that includes particles comprising any compound identified above.The powder may serve as part or all of a cathode active material (i.e.,the cathode active material includes the powder).

The compounds and powders can be in a cathode active material forlithium ion batteries, as described herein. These cathode activematerials assist energy storage by releasing and storing lithium ionsduring, respectively, charging and discharging of a lithium-ion battery.

Without wishing to be limited to a particular mechanism or mode ofaction, the compounds can improve volumetric energy density, energyretention, and/or cyclability of cathode active materials during chargeand discharge of battery cells. The compounds can improve the thermalstability of the cathode active materials.

In some variations, the particles have a mean particle diameter greaterthan or equal to a first lower limit. In some variations, the particlehas a mean diameter of at least 5 μm. In some variations, the particlehas a mean diameter of at least 10 μm. In some variations, the particlehas a mean diameter of at least 15 μm. In some variations, the particlehas a mean diameter of at least 20 μm. In some variations, the particlehas a mean diameter of at least 25 μm.

In some variations, the particles have a mean particle diameter lessthan or equal to a first upper limit. In some variations, the particlehas a mean diameter of less than or equal to 30 μm. In some variations,the particle has a mean diameter of less than or equal to 25 μm. In somevariations, the particle has a mean diameter of less than or equal to 20μm. In some variations, the particle has a mean diameter of less than orequal to 15 μm. In some variations, the particle has a mean diameter ofless than or equal to 10 μm. In some variations, the particle has a meandiameter of less than or equal to 5 μm.

It will be understood that the first lower and upper limits may becombined in any variation as above to define a first range for the meanparticle diameter. For example, and without limitation, the meanparticle diameter may range from 10 μm to 20 μm. In another non-limitingexample, the mean particle diameter may range from 20 μm to 25 μm. Otherranges are possible. The particles having the aforementioned meanparticle diameters, whether characterized by the first lower limit, thefirst upper limit, or both (i.e., the first range), may be processedaccording to a co-precipitation method.

In some variations, the particles have a mean particle diameter greaterthan or equal to a second lower limit. In some variations, the particlehas a mean diameter of at least 200 nm. In some variations, the particlehas a mean diameter of at least 300 nm. In some variations, the particlehas a mean diameter of at least 400 nm. In some variations, the particlehas a mean diameter of at least 500 nm. In some variations, the particlehas a mean diameter of at least 600 nm. In some variations, the particlehas a mean diameter of at least 700 nm.

In some variations, the particles have a mean particle diameter lessthan or equal to a second upper limit. In some variations, the particlehas a mean diameter of less than or equal to 800 nm. In some variations,the particle has a mean diameter of less than or equal to 700 nm. Insome variations, the particle has a mean diameter of less than or equalto 600 nm. In some variations, the particle has a mean diameter of lessthan or equal to 500 nm. In some variations, the particle has a meandiameter of less than or equal to 400 nm. In some variations, theparticle has a mean diameter of less than or equal to 300 nm.

It will be understood that the second lower and upper limits may becombined in any variation as above to define a second range for the meanparticle diameter. For example, and without limitation, the meanparticle diameter may range from 300 nm to 500 nm. In anothernon-limiting example, the mean particle diameter may range from 400 nmto 800 nm. Other ranges are possible. The particles having theaforementioned mean particle diameters, whether characterized by thesecond lower limit, the second upper limit, or both (i.e., the secondrange), may be processed according to a sol-gel method.

In some variations, the particles are secondary particles are formed ofagglomerated primary particles. The agglomerated primary particles maybe sintered together. In some instances, the secondary particles have amean particle diameter greater than or equal to a lower limit.Non-limiting examples of the lower limit include 15 μm, 20 μm, and 25μm. In some instances, the secondary particles have a mean particlediameter less than or equal to an upper limit. Non-limiting examples ofthe upper limit include 30 μm, 25 μm, and 20 μm. It will be understoodthat the lower and upper limits may be combined in any variation asabove to define a range for the mean particle diameter. For example, andwithout limitation, the mean particle diameter may range from 15 μm to20 μm. In another non-limiting example, the mean particle diameter mayrange from 20 μm to 25 μm. Other ranges are possible.

In some variations, a single primary particle occupies a percentage of avolume occupied by a corresponding secondary particle. In someinstances, the percentage is greater or equal to a lower limit. In somevariations, a single primary particle occupies at least 30% of a volumeoccupied by a corresponding secondary particle. In some variations, asingle primary particle occupies at least 35% of a volume occupied by acorresponding secondary particle. In some variations, a single primaryparticle occupies at least 40% of a volume occupied by a correspondingsecondary particle. In some variations, a single primary particleoccupies at least 45% of a volume occupied by a corresponding secondaryparticle. In some variations, a single primary particle occupies atleast 50% of a volume occupied by a corresponding secondary particle. Insome variations, a single primary particle occupies at least 55% of avolume occupied by a corresponding secondary particle. In somevariations, a single primary particle occupies at least 60 of a volumeoccupied by a corresponding secondary particle. In some variations, asingle primary particle occupies at least 65% of a volume occupied by acorresponding secondary particle.

In some variations, a single primary particle occupies less than orequal to 70% of a volume occupied by a corresponding secondary particle.In some variations, a single primary particle occupies less than orequal to 65% of a volume occupied by a corresponding secondary particle.In some variations, a single primary particle occupies less than orequal to 60% of a volume occupied by a corresponding secondary particle.In some variations, a single primary particle occupies less than orequal to 55% of a volume occupied by a corresponding secondary particle.In some variations, a single primary particle occupies less than orequal to 50% of a volume occupied by a corresponding secondary particle.In some variations, a single primary particle occupies less than orequal to 45% of a volume occupied by a corresponding secondary particle.In some variations, a single primary particle occupies less than orequal to 40% of a volume occupied by a corresponding secondary particle.In some variations, a single primary particle occupies less than orequal to 35% of a volume occupied by a corresponding secondary particle.

It will be understood that the lower and upper limits may be combined inany variation as above to define a range for the percentage. Forexample, and without limitation, the percentage may range from 30-50%.However, other ranges are possible.

As described herein, the larger particle sizes, and percentage ofsecondary particles occupied by a singled primary particle, can beformed by using higher sintering temperatures. Without wishing to beheld to a particular mechanism or mode of action, in some instances theparticles do not fracture as readily, and thereby can provide increasedstability than conventional particles.

Including Mn and/or Al in the compound in place of Co, altering theamount of Li, and/or including an Al₂O₃ coating can reduce, or reducethe likelihood of, a destabilizing phase transition. Without wishing tobe limited to a particular mechanism or mode of action, the additionalelements also give greater oxidative stability to the compounds athigher battery upper cut-off voltages. In some variations, thecompounds, particles, and/or cathode active materials can have increasedstability for at least 4.4V vs. Li/Li⁺.

In some variations, the particles have increased particle strength. Theincreased particle strength results in increased energy retention whenthe particles are used in a cathode active material.

In some variations, increased amount of manganese in cathode activematerials provides for improved battery stability. In some variations,the increased amount of Mn increases the onset temperature ofdecomposition. In some variations, increased amounts of Mn can result inreduced amount of heat release at a decomposition temperature of thecompound.

In some variations, the cathode active materials have a first-cycledischarge energy of at least 700 Wh/kg. In some variations, the cathodeactive materials have a first-cycle discharge energy of at least 725Wh/kg. In some variations, the cathode active materials have afirst-cycle discharge energy of at least 750 Wh/kg. In some variations,the cathode active materials have a first-cycle discharge energy of atleast 775 Wh/kg. In some variations, the cathode active materials have afirst-cycle discharge energy of at least 800 Wh/kg. In some variations,the cathode active materials have a first-cycle discharge energy of atleast 825 Wh/kg. In some variations, the cathode active materials have afirst-cycle discharge energy of at least 850 Wh/kg. In some variations,the cathode active materials have a first-cycle discharge energy of atleast 875 Wh/kg.

In some variations, the cathode active materials have a first-cycledischarge capacity of at least 180 mAh/g. In some variations, thecathode active materials have a first-cycle discharge capacity of atleast 185 mAh/g. In some variations, the cathode active materials have afirst-cycle discharge capacity of at least 190 mAh/g. In somevariations, the cathode active materials have a first-cycle dischargecapacity of at least 195 mAh/g. In some variations, the cathode activematerials have a first-cycle discharge capacity of at least 200 mAh/g.In some variations, the cathode active materials have a first-cycledischarge capacity of at least 205 mAh/g. In some variations, thecathode active materials have a first-cycle discharge capacity of atleast 210 mAh/g. In some variations, the cathode active materials have afirst-cycle discharge capacity of at least 215 mAh/g.

In some variations, the cathode active materials have an energy capacityretention of at least 65% after 52 charge-discharge cycles. In somevariations, the cathode active materials have an energy capacityretention of at least 67% after 52 charge-discharge cycles. In somevariations, the cathode active materials have an energy capacityretention of at least 69% after 52 charge-discharge cycles. In somevariations, the cathode active materials have an energy capacityretention of at least 71% after 52 charge-discharge cycles. In somevariations, the cathode active materials have an energy capacityretention of at least 73% after 52 charge-discharge cycles. In somevariations, the cathode active materials have an energy capacityretention of at least 75% after 52 charge-discharge cycles. In somevariations, the cathode active materials have an energy capacityretention of at least 77% after 52 charge-discharge cycles. In somevariations, the cathode active materials have an energy capacityretention of at least 79% after 52 charge-discharge cycles. In somevariations, the cathode active materials have an energy capacityretention of at least 81% after 52 charge-discharge cycles. In somevariations, the cathode active materials have an energy capacityretention of at least 83% after 52 charge-discharge cycles.

The compounds, powders, and cathode active materials can be used inbatteries as described herein. The materials can be used in electronicdevices. An electronic device herein can refer to any electronic deviceknown in the art, including a portable electronic device. For example,the electronic device can be a telephone, such as a cell phone, and aland-line phone, or any communication device, such as a smart phone,including, for example an iPhone®, an electronic email sending/receivingdevice. The electronic device can also be an entertainment device,including a portable DVD player, conventional DVD player, Blue-Ray diskplayer, video game console, music player, such as a portable musicplayer (e.g., iPod®), etc. The electronic device can be a part of adisplay, such as a digital display, a TV monitor, an electronic-bookreader, a portable web-browser (e.g., iPad®), watch (e.g., AppleWatch),or a computer monitor. The electronic device can also be a part of adevice that provides control, such as controlling the streaming ofimages, videos, sounds (e.g., Apple TV®), or it can be a remote controlfor an electronic device. Moreover, the electronic device can be a partof a computer or its accessories, such as the hard drive tower housingor casing, laptop housing, laptop keyboard, laptop track pad, desktopkeyboard, mouse, and speaker. The battery and battery packs can also beapplied to a device such as a watch or a clock. The components poweredby a battery or battery pack can include, but are not limited to,microprocessors, computer readable storage media, in-put and/or out-putdevices such as a keyboard, track pad, touch-screen, mouse, speaker, andthe like.

EXAMPLES

The following examples are for illustration purposes only. It will beapparent to those skilled in the art that many modifications, both tomaterials and methods, may be practiced without departing from the scopeof the disclosure.

Example 1—Wet Impregnation to Form an Al₂O₃ Coating

De-ionized water (Millipore ultra-pure water, 18 MΩ*cm) was addeddrop-wise to 10 g of base powder (i.e., 10 g ofLi_(1.04)Co_(0.96)Mn_(0.04)O_(2.04) base powder) while stirring. Whenthe powder was wetted yet still loose, the stirring was stopped. (Theaddition of de-ionized water was stopped before the powder formed awatery or sticky mass.) A ratio, R, was then calculated that equaled anamount (either weight or volume) of added water divided by an amount ofbase powder. The amount of water needed to wet the powder to a suitabledampness depends on the surface area of the base powder used. Ingeneral, higher surface areas require more water.

Next, a quantity (e.g., weight) of base powder was selected. An amountof aluminum salt precursor (e.g., aluminum nitrate nonahydrate) wasdetermined that would correspond to a desired level of Al₂O₃ coating onthe desired quantity base powder (e.g., 0.1 wt. %). An amount ofde-ionized water was then calculated using the ratio (i.e., multiplyingR times the weight of the base powder). TABLE 1 presents types andquantities of base powder, solvent (i.e., de-ionized water), andaluminum salt precursor.

The quantities given in TABLE 1 were then measured, including thede-ionized water whose amount was predetermined. Aluminum nitratenonahydrate was dissolved in the de-ionized water to form a clearsolution. Drops of the clear solution were added to the base powder in aglass container under stirring. Once the clear solution was consumed,the base powder was stirred continuously for a few minutes to ensurewell-mixing. A wetted, loose powder was formed.

The wetted, loose powder was dried in an oven overnight at 80° C. Thedried powder was then transferred to an Al₂O₃ crucible and heat-treatedat 120° C. for 2 hours. This heat treatment was followed by a subsequentheat treatment at 500° C. for 4 hours in stagnant air. The heat-treatedpowder was passed through 325-mesh sieve. Occasionally, light grindingwith mortar and pestle was needed to break up agglomerated portions ofthe heated-treated powder.

TABLE 1 Materials for 0.1 wt. % Al₂O₃ Coating on 10 gLi_(1.04)Co_(0.96)Mn_(0.04)O₂ Material Reagent/Material Quantity UsedBase powder Li_(1.04)Co_(0.96)Mn_(0.04)O₂   10 g Solvent (for dissolvingcoating De-ionized water ~0.9-1 ml or g precursor) Coating PrecursorAl(NO₃)₃•9H₂O 0.075 g

Example 2—Wet Impregnation to Form an AlF₃ Coating

A ratio, R, was determined according to procedures described in relationto Example 1.

Next, a quantity (e.g., weight) of base powder was selected. An amountof aluminum salt precursor (e.g., aluminum nitrate nonahydrate) andfluoride salt precursor (e.g., ammonium fluoride) was determined thatwould correspond to a level of AlF₃ coating on the desired quantity basepowder (e.g., 0.1 wt. %). To ensure complete reaction, the amount offluoride salt precursor was doubled relative to a stoichiometric amountof fluoride in AlF₃ (i.e., a mole ratio of Al to F was selected to be1:6). A needed amount of de-ionized water was then calculated using theratio (i.e., multiplying R times the weight of the base powder).

Aluminum nitrate nonahydrate was dissolved in a first portion of thede-ionized water to form a first clear solution. Ammonium fluoride wasdissolved in a second portion of de-ionized water to form a second clearsolution. The base powder was transferred to a glass container and dropsof the first clear solution were added quickly therein (i.e., to “flood”the base powder). The base powder was stirred for 2 minutes and thedried at 105° C. to yield a powder cake.

The powder cake was broken up into a loose powder (e.g., with a mortarand pestle) and then transferred into a fresh glass container. The freshglass container was gently tapped to pack the loose powder therein. Thesecond clear solution was quickly added to the packed powder whilestirring (i.e., similar to the first clear solution). This mixture wasstirred for 2 minutes before drying at 105° C. The dried powder wastransferred to an alumina saggar for heat treatment for 2 hours at 120°C. in flowing nitrogen. The heat-treated powder was then heated at 400°C. for 5 hours, resulting in a heat-treated powder cake. Theheat-treated powder cake readily broke apart and was lightly ground andsieved through a 325 mesh.

Example 3—Wet Impregnation to Form an AlPO₄ Coating

A predetermined amount of base powder (i.e.,Li_(1.04)Co_(0.96)Mn_(0.04)O₂) was weighed out in a glass container. Anamount of aluminum and phosphate precursor needed for a desired amountof AlPO₄ coating (e.g., 5 wt. %) was calculated based on the weighedamount of base powder. The aluminum precursor used included variousaluminum salts such as aluminum nitrate, aluminum acetate, or otheraluminum salt soluble in water or alcohol. The phosphate precursor usedwas either ammonium dihydrogen phosphate (NH₄H₂PO₄), diammonium hydrogenphosphate [(NH₄)₂HPO₄], or a combination of both. A mole ratio of Al toP was kept between 0.9 and 1.1. The aluminum precursor and phosphateprecursor were dissolved separately in a small amount of water oralcohol to form solutions. The two solutions were then mixed together.The pH of the mixed solution was adjusted by varying a ratio of theammonium phosphate salts to prevent precipitation. The mixed solutionwas added drop-wise onto the base powder while stirring with a glass rodor spatula. The volume of solution was such that the base powder wasincipiently wet and well mixed (i.e., exhibited a damp consistency).After drying at 50-80° C., the dried base powder was heat-treated at700° C. for 5 h in stagnant air.

Example 4—Wet Impregnation to Form a Co₃(PO₄)₂ Coating

A predetermined amount of base powder (i.e.,Li_(1.04)Co_(0.96)Mn_(0.04)O₂) was weighed out in a glass container. Anamount of cobalt and phosphate precursor needed for a desired amount ofCo₃(PO₄)₂ coating (e.g., 5 wt. %) was calculated based on the weighedamount of base powder. The cobalt precursor used included various cobaltsalts such as cobalt nitrate, cobalt acetate, or other cobalt saltsoluble in water or alcohol. The phosphate precursor used was eitherammonium dihydrogen phosphate (NH₄H₂PO₄), diammonium hydrogen phosphate[(NH₄)₂HPO₄], or a combination of both. A mole ratio of Co to P was keptbetween 1.4 and 1.6. The cobalt precursor and the phosphate precursorwere dissolved separately in a small amount of water or alcohol to formsolutions. The two solutions were then mixed together. A pH of the mixedsolution was adjusted by varying a ratio of the ammonium phosphate saltsto prevent precipitation. The mixed solution was added drop-wise ontothe base powder while stirring with a glass rod or spatula. The volumeof solution added was such that the base powder was incipiently wet andwell mixed (i.e., exhibited a damp consistency). After drying at 50-80°C., the dried base powder was then heat-treated at 700° C. for 5 h instagnant air.

Example 5—Wet Impregnation to Form a Li—Al₂O₃ Coating

A predetermined amount of base powder (i.e.,Li_(1.04)Co_(0.96)Mn_(0.04)O₂) was weighed out into a glass beaker. Anamount of aluminum precursor needed for the desired amount of coating(e.g., 0.5 wt. %) was calculated based on the weighed amount of basepowder. The aluminum precursor included various aluminum salts such asaluminum nitrate, aluminum acetate, or other aluminum salts soluble inwater or alcohol. The aluminum precursor was dissolved in a small amountof water or alcohol to form a first clear solution. A desired amount oflithium precursor was calculated using a molar ratio of Li to Al between0.25 and 1.05. The lithium precursor used was lithium hydroxide, lithiumnitrate, lithium acetate, or other lithium salts soluble in water oralcohol. The desired amount of lithium precursor was dissolved in asmall amount of water or alcohol to form a second clear solution. Thefirst and second clear solutions were mixed together. This mixedsolution was then added drop-wise to the base powder while stirring. Thevolume of solution added was such that the base powder becameincipiently wet but not watery (i.e., exhibited a damp consistency).After drying at 50-80° C., the dried base powder was then heat-treatedto 500° C. for 4 h in stagnant air. The pH of the first clear solution(i.e., the aluminum solution) can also be varied to improve coatingproperties such as coating density and uniformity.

Example 6—Wet Impregnation to Form a Li—Co₃(PO₄)₂ Coating

A predetermined amount of base powder (i.e.,Li_(1.04)Co_(0.96)Mn_(0.04)O₂) was weighed out into a glass beaker. Anamount of cobalt, phosphate, and lithium precursors needed for a desiredamount of coating (e.g., 0.5 wt. %) was calculated based on the weighedamount of base powder. The cobalt precursor included various cobaltsalts such as cobalt nitrate, cobalt acetate, or other cobalt saltssoluble in water or alcohol. The phosphate precursor used was eitherammonium dihydrogen phosphate (NH₄H₂PO₄), diammonium hydrogen phosphate[(NH₄)₂HPO₄], lithium phosphates, or combinations of such. A mole ratioof Co to P is kept between 1.4 and 1.6. A desired amount of lithiumprecursor was calculated using a molar ratio of Li to Co between 0.3 and1.05. The lithium precursor used was lithium hydroxide, lithium nitrate,lithium acetate, or other lithium salts soluble in water or alcohol. Thecobalt, phosphate and lithium precursors were dissolved separately in asmall amount of water or alcohol to form corresponding clear solutions.The three solutions were then mixed together. This mixed solution wasthen added drop-wise to the base powder while stirring. The volume ofsolution added was such that the base powder became incipiently wet butnot watery (i.e., exhibited a damp consistency). After drying at 50-80°C., the dried base powder was heat-treated to 700° C. for 5 h instagnant air.

Example 7—Suspension Processing to Form an Al₂O₃ Coating

An aqueous solution of Al(NO₃)₃ was mixed with a suspension of basepowder (Li_(1.02)Co_(0.96)Mn_(0.04)O₂) and then pumped into astirred-tank reactor. While stirring, an ammonia solution was used tohold a reaction pH value at 9.3 using a feedback pump. The suspensionwas stirred for 2 h, filtered, dried, and calcined at 400° C. for 5 h inair.

Example 8—Suspension Processing to Form a Co₃(PO₄)₂ Coating

A first aqueous solution of Co(NO₃)₃ and a second aqueous solution ofammonium dihydrogen solution were pumped into a suspension of basepowder (Li_(1.02)Co_(0.96)Mn_(0.04)O₂) in a stirred-tank reactor. Thecombined volume was stirred for 2 h, filtered, and dried. The driedpowder was calcined at 700° C. for 5 h in air.

Example 9—Suspension Processing to Form an AlPO₄ Coating

A first aqueous solution of Al(NO₃)₃ and a second solution of ammoniumdihydrogen phosphate were pumped into a suspension of base powder(Li_(1.02)Co_(0.96)Mn_(0.04)O₂) in a stirred-tank reactor. The combinedvolume was stirred for 2 h, filtered, and dried. The dried powder wascalcined at 700° C. for 5 h in air.

Example 10—Dry Processing to Form an Al₂O₃ Coating

A predetermined amount of base powder (Li_(1.02)Co_(0.96)Mn_(0.04)O₂)was weighed out and poured into a dry coater (Nobilta, NOB-130, HosokawaMicron Ltd). Next, nanocrystalline Al₂O₃ powder was weighed outaccording to a desired amount of coating on the predetermined basepowder (e.g., 0.5 wt. %). The weighed nanocrystalline Al₂O₃ powder waspoured into the dry coater. The dry coater included a high speed rotarymixer that bonds, via a mechanofusion process, particles of thenanocrystalline Al₂O₃ powder to particles in the base powder (i.e.,along a surface thereof). For a 0.5 wt. % coating, 2.5 g ofnanocrystalline Al₂O₃ powder was mixed thoroughly with 500 g of basepowder. The speed was controlled at 4000 rpm. After 5 min, anAl₂O₃-coated base powder was formed.

Example 11—Dry Processing to Form an AlF₃ Coating

A predetermined amount of base powder (Li_(1.02)Co_(0.96)Mn_(0.04)O₂)was weighed out and poured into a dry coater (Nobilta, NOB-130, HosokawaMicron Ltd). Next, nanocrystalline AlF₃ powder was weighed out accordingto a desired amount of coating on the predetermined base powder (e.g.,0.1 wt. %). The weighed nanocrystalline AlF₃ powder was poured into thedry coater. For a 0.1 wt. % coating, 0.5 g of AlF₃ was mixed thoroughlywith 500 g of base powder. The speed was controlled at 4000 rpm. After 5min, an AlF₃-coated base powder was formed.

Example 12—Dry Processing to Form a Coating of Al₂O₃ and AlF₃

A predetermined amount of base powder (Li_(1.02)Co_(0.96)Mn_(0.04)O₂)was weighed out and poured into a dry coater (Nobilta, NOB-130, HosokawaMicron Ltd). Next, nanocrystalline Al₂O₃ powder and nanocrystalline AlF₃powder were weighed out according to a desired amount of coating on thepredetermined base powder (e.g., 0.1 wt. %). The weighed nanocrystallinepowders were poured into the dry coater. For a 0.1 wt. % coating, 0.25 gof Al₂O₃ and 0.05 g of AlF₃ were mixed thoroughly with 500 g of basepowder. The speed was controlled at 4000 rpm. After 5 min, a base powdercoated with Al₂O₃ and AlF₃ was formed.

Example 13—Powder Characterization

The morphology, composition, and electrochemical performance of certaincoated powders were evaluated with scanning electron microscopy (SEM),inductively-coupled plasma optical emission spectroscopy (ICP-OES), anda Maccor tester.

FIGS. 3A-3C present a series of scanning electron micrographs showing,respectively, a base powder, a 0.1 wt. % AlF₃-coated base powder, and a0.1 wt. % Al₂O₃-coated base powder, according to an illustrativeembodiment. The base powder corresponds to particles comprisingLi_(1.02)Co_(0.96)Mn_(0.04)O₂. Only a subtle difference is shown for thepowders before and after wet impregnation. Compared to an uncoatedpowder, i.e., FIG. 3A, surfaces of the coated powders appear furry andrough as indicated by stains or bumps, i.e., FIGS. 3B and 3C.

Quantities of Al₂O₃ and AlF₃ coated on base powder samples weredetermined with ICP-OES. TABLES 2 and 3 show the results for,respectively, Al₂O₃ and AlF₃ wet-impregnated base powders. A comparisonof target coating levels with measured values indicates that themeasured values match very well with their corresponding target valuesfor coating levels ≧0.2 wt. %.

TABLE 2 ICP-OES results of Al₂O₃-coated and uncoated base powdersLi/(Co + Mn/(Co + Al/(Co + Co/(Co + Mn + Ni) Mn + Ni) Mn + Ni) Mn + Ni)Sample No. Target Al2O3, wt % Measured Al2O3 Value ± Value ± Value ±Value ± XW189a 0.05 0.0775 0.989 0.002 0.0396 0.0001 0.0018 0.0001 0.963E−04 XW189b 0.1 0.1323 0.988 0.002 0.0396 0.0001 0.0028 0.0002 0.963E−04 XW189c 0.5 0.5083 0.988 0.002 0.0396 9E−05 0.0102 0.0006 0.9594E−04 XW190a 0.5 0.4648 0.987 0.002 0.0395 8E−05 0.0095 0.0008 0.9596E−04 Uncoated 0 1.008 0.002 0.0397 0.0001 0.003 0.0002 0.96 3E−04 HW168

TABLE 3 ICP-OES results of AlF₃-coated and uncoated base powdersLi/(Co + Mn/(Co + Al/(Co + Co/(Co + Mn + Ni) Mn + Ni) Mn + Ni) Mn + Ni)Sample No. Target coagting, wt % Measured AlF3, wt % Value ± Value ±Value ± Value ± CL130a 0.05 0.103 0.9877 0.002 0.03955 0.00012 0.001450.00011 0.9597 0.0003 CL129b 0.1 0.156 0.9871 0.002 0.03956 0.000120.00205 0.00016 0.9601 0.0003 CL125 0.2 0.224 0.9867 0.0021 0.039530.00008 0.00307 0.00025 0.9595 0.0006 CL129a 0.2 0.221 0.9853 0.00210.03951 0.00008 0.00304 0.00025 0.9595 0.0006 Uncoated 0 1.0083 0.00210.03965 0.00012 0.00301 0.00023 0.9596 0.0003 HW168

Example 14

Electrochemical tests were conducted on 2032 coin half-cells having acathode active material loading of approximately 15 mg/cm². Anelectrolyte used by the 2032 coin half-cells included 1.2 M LiPF₆ in anEC:EMC solvent of 3:7 ratio by weight. The cells were placed on a MaccorSeries 2000 tester and cycled in galvanostatic mode at room temperaturewith the voltage windows of 4.5V to 2.75V. A series of electrochemicaltests of formation, rate, and cycling were conducted under each voltagewindow. During formation testing, a constant current (0.2 C) was appliedto the cell during the charge process, followed by a constant voltagecharge until the current was equal to or less than 0.05 C. Then, thecells were discharged at constant current (0.2 C) until the end ofdischarge. Charging and discharging of the cells were repeated threetimes. During rate testing, the charging rate was fixed to 0.7 C for allthe rate tests, and then followed by constant voltage charge until thecurrent was equal to or less than 0.05 C. Five different discharge ratesof 0.1 C, 0.2 C, 0.5 C, 1 C, and 2 C were applied until the cells werecompletely discharged. Three cycles were conducted for each rate.Finally, 50 cycles were conducted to investigate cycle life. The samecharging conditions as those of the rate test were applied. Thedischarge rate was fixed to 0.5 C for all the cycles.

Here we present the cycle data for the base powderLi_(1.04)Co_(0.96)Mn_(0.04)O₂ and the two highest performing coatedsamples (Li_(1.04)Co_(0.96)Mn_(0.04)O₂—Al₂O₃ 0.05 wt % andLi_(1.04)Co_(0.96)Mn_(0.04)O₂—AlF₃ 0.1 wt %).

FIG. 4 presents a plot of data representing a performance of three coinhalf-cells, each incorporating a single cathode active material, duringa first cycle of charging and discharging, according to an illustrativeembodiment. The single cathode active material for each of three coinhalf-cells corresponds to, respectively, the base powderLi_(1.04)Co_(0.96)Mn_(0.04)O₂ (i.e. “HW168”), 0.05 wt. % Al₂O₃-coatedLi_(1.04)Co_(0.96)Mn_(0.04)O₂, (i.e., “HW168-Al₂O₃ 0.05 wt. %) and 0.1wt. % AlF₃-coated Li_(1.04)Co_(0.96)Mn_(0.04)O₂ (i.e., “HW168-AlF₃ 0.1wt. %). The performance of the three coin half-cells is characterized bytwo bars: A leftmost bar indicates a first cycle charge capacity and arightmost bar indicates a first cycle discharge capacity.

In FIG. 4, the presence of coatings in the cathode active materialslightly reduces the first cycle charge capacity and discharge capacityas both the Al₂O₃- and AlF₃-coated variants show a 4 mAh/g reducedcapacity relative to the uncoated variant. This value is higher thanwhat was expected for such small amount of coating. Such reduction incapacity may be attributed to the loss of lithium during the coatingprocess, as indicated by the ICP-OES data in TABLES 3 and 4. However,the performance shown by FIG. 4, which is an initial performance, is notrepresentative of coin half-cell performance in subsequent charge anddischarge cycles.

FIGS. 5 and 6 present a plot of data representing a change in capacity,over extended cycling, of the three coin half-cells of FIG. 4, accordingto an illustrative embodiment. FIGS. 7 and 26 present a plot of datarepresenting a change in energy density, over extended cycling, of thethree coin half-cells of FIG. 4, according to an illustrativeembodiment. FIGS. 5 and 7 correspond to rate testing and FIGS. 6 and 8correspond to life testing.

FIG. 5 shows that, up to a IC rate, the presence of coatings did notaffect the performance of coin half-cells incorporatingLi_(1.04)Co_(0.96)Mn_(0.04)O₂, Al₂O₃-coatedLi_(1.04)Co_(0.96)Mn_(0.04)O₂, and AlF₃-coatedLi_(1.04)Co_(0.96)Mn_(0.04)O₂. Their capacities are similar up to a ICrate (i.e., for C/10, C/5, C/2, and IC). The coin half-cellcorresponding to Al₂O₃-coated Li_(1.04)Co_(0.96)Mn_(0.04)O₂ showed areduced (relative) performance at a 2 C rate.

Coating benefits are more clearly highlighted in FIG. 6, which presentslife testing. Coin half-cells corresponding to coatedLi_(1.04)Co_(0.96)Mn_(0.04)O₂ variants show improved capacities relativeto uncoated Li_(1.04)Co_(0.96)Mn_(0.04)O₂. the coin half-cellsassociated with coated Li_(1.04)Co_(0.96)Mn_(0.04)O₂ lose only 4-5mAh/g.

The coin half-cell incorporating uncoated Li_(1.04)Co_(0.96)Mn_(0.04)O₂started with lower capacity, i.e., relative to those incorporatingcoated Li_(1.04)Co_(0.96)Mn_(0.04)O₂, because this cell half-cell wasalready cycled 19 times after the aging and the rate tests. Suchpre-aging resulted in quicker degradation than those not pre-aged (i.e.,those utilizing coated Li_(1.04)Co_(0.96)Mn_(0.04)O₂). More than 15mAh/g of capacity was lost over a 26 life cycle test.

A similar trend was observed in FIGS. 7 and 8 for energy density asdescribed in relation to FIGS. 5 and 6. However, the coin half-cellassociated with uncoated Li_(1.04)Co_(0.96)Mn_(0.04)O₂ starts at a lowerenergy density than those the two coated sample (FIGS. 7 and 8). TheAlF₃-coated samples maintain a higher energy density than theAl₂O₃-coated sample.

FIGS. 9 and 10 present plots of data representing to charge-dischargeprofiles for each the three coin half-cells of FIG. 4. FIG. 9 presentsrate testing and FIG. 10 presents life testing. These profilesdemonstrate an advantage of the coatings disclosed herein. The shape ofcurves was more preserved for coin half-cells incorporating Al₂O₃- andAlF₃-coated Li_(1.04)Co_(0.96)Mn_(0.04)O₂ than those base powderLi_(1.04)Co_(0.96)Mn_(0.04)O₂. Indeed, the variant corresponding touncoated Li_(1.04)Co_(0.96)Mn_(0.04)O₂ shows the fastest decay incapacity with increasing cycle number.

FIGS. 11 and 12 present plots of data representing dQ/dV profiles foreach the three coin half-cells of FIG. 4. FIG. 11 presents rate testingand FIG. 12 presents life testing. Curves in each profile were plottedevery 5 cycles for both rate and life tests. A reduction peak atapproximately 3.85V characterizes a structural stability of the cathodeactive material in each coin half-cell during progressive cycling.

A degradation of the cathode active material (i.e., structuralinstability) is reflected by shifting and broadening of the reductionpeak toward lower voltages. During rate testing, the coin half-cellcorresponding to base powder Li_(1.04)Co_(0.96)Mn_(0.04)O₂ showed thehighest degradation with a relatively fast shift away from 3.85V and alarge peak broadening. In contrast, the coin half-cells corresponding toits coated variants showed slower shifts and weaker broadening. Peakshifting and broadening are less evident during rate testing than lifetesting. This behavior results from lower amounts of lithium ions beingcycled back and forth as a charge/discharge rate progressivelyincreases. During the life test, the coin half-cell incorporatingbaseline LiCoO₂ showed further degradation while those incorporatingLi_(1.04)Co_(0.96)Mn_(0.04)O₂ and its coated variants showed almost nodegradation.

Example 15—Cathode Active Materials by Co-Precipitation Methods

A 3.5-liter stirred tank reactor was filled with distilled water andheated to 60° C. A flow of nitrogen gas was introduced into the tankreactor while stirring the distilled water at a rate of 1100 rpm.Separately, manganese and cobalt sulfate were dissolved in distilledwater to produce a first aqueous solution having a total concentrationof 2.0M and a predetermined molar ratio (i.e., [Mn]:[Co]). The ratioincluded representative examples, such as [Mn]:[Co]=0.00:1.00,0.04:0.96, 0.07:0.93, 0.10:0.90, 0.16:0.84, and 0.28:0.72. The firstaqueous solution was continuously dripped into distilled water of thetank reactor at a flow rate of 100 ml/h to produce a combined aqueoussolution. The pH of the combined aqueous solution was fixed at 11.5 byadding a second aqueous solution of sodium hydroxide and ammonia using apH controller coupled to a pump. Over a 300 hour run-time, particlesnucleated and grew in the combined aqueous solution, thereby formingfinal precursor particles. The final precursor particles were washed,filtered, and dried at 175° C. for 12 h.

The final precursor particles were used to form cathode active materialsof composition LiMn_(x)Co_(1−x)O₂ where x and 1−x correspond to thepredetermined molar ratio, i.e., [Mn]:[Co]=[x]:[1−x]. A solid-statereaction was carried out with Li₂CO₃ powder and powders of the finalprecursor particles. The molar ratio of Li₂CO₃ and the final precursorparticles with was varied to yield cathode active materials havingvariations in ratios of [Li]:[Mn_(x)Co_(1−x)] (i.e., ratios of lithiumto total transition-metal content). The Li₂CO₃ powder and powders of thefinal precursor particles were blended in an orbital mixer to produce amixed powder. Following blending, the mixed powder was transferred to analumina tray and heated in flowing air at 700° C. for 10 hours. The ramprate of the furnace was 5° C. per minute. After heating at 700° C., themixed powder, now reacted, was allowed to cool in the furnace to ambienttemperature via natural heat losses. The resulting intermediate powderwas ground by mortar and pestle, sieved, and re-fired at 1050° C. inflowing air for 15 hours. The ramp rate was 5° C. per minute, and afterfiring, the resulting sintered powder was allowed to cool in the furnaceto ambient temperature via natural heat losses. The sintered powder wasbroken up, ground by mortar and pestle, and sieved to produce a cathodeactive material. Samples of the cathode active materials werecharacterized by powder X-ray diffraction using a Bruker D8 (see FIGS.20 and 21).

Representative examples of cathode active materials prepared by theabove-described co-precipitation method include LiCoO₂,Li_(0.987)Co_(0.96)Mn_(0.04)O₂, Li_(1.050)Co_(0.96)Mn_(0.04)O₂,Li_(1.074)Co_(0.96)Mn_(0.04)O₂, Li_(1.081)Co_(0.96)Mn_(0.04)O₂,Li_(1.089)Co_(0.96)Mn_(0.04)O₂, Li_(0.981)Co_(0.93) Mn_(0.07)O₂,Li_(1.050)Co_(0.93)Mn_(0.07)O₂, Li_(0.984)Co_(0.90)Mn_(0.10)O₂,Li_(1.065)Co_(0.90)Mn_(0.01)O₂, Li_(1.100)Co_(0.90)Mn_(0.10)O₂,Li_(1.110)Co_(0.90)Mn_(0.10)O₂, Li_(1.158)Co_(0.90)Mn_(0.10)O₂,Li_(0.975)Co_(0.84)Mn_(0.16)O₂, Li_(1.050)Co_(0.84)Mn_(0.16)O₂,Li_(1.114)Co_(0.84)Mn_(0.16)O₂, Li₀₉₉₄Co_(0.78)Mn_(0.22)O₂,Li_(1.100)Co_(0.78)Mn_(0.22)O₂, Li_(1.197)Co_(0.78)Mn_(0.22)O₂,Li_(0.973)Co_(0.72)Mn_(0.28)O₂, Li_(1.087)Co_(0.72)Mn_(0.28)O₂,Li_(1.190)Co_(0.72)Mn_(0.28)O₂, and Li_(1.247)Co_(0.72)Mn_(0.28)O₂.

FIG. 19 presents scanning electron micrographs of cathode activematerials prepared according to the co-precipitation method describedabove. The micrographs indicate secondary particles formed ofdensely-sintered primary particles. Such densely-sintered secondaryparticles are typical for cathode active materials prepared by theco-precipitation method. The compositions of the cathode activematerials correspond to Li_(0.96)Co_(0.93) Mn_(0.07)O₂, Li_(0.9)Co_(0.93) Mn_(0.07)O₂, and Li_(1.00)Co_(0.93)Mn_(0.07)O₂.

FIG. 20 presents X-ray powder diffraction patterns for cathode activematerials represented by compositions of Li_(1.074)Co_(0.96)Mn_(0.04)O₂,Li_(1.081)Co_(0.96)Mn_(0.04)O₂, Li_(1.089)Co_(0.96)Mn_(0.04)O₂,Li_(1.065)Co_(0.90)Mn_(0.10)O₂, Li_(1.110)Co_(0.90)Mn_(0.10)O₂,Li_(1.158)Co_(0.90)Mn_(0.10)O₂, Li_(0.975)Co_(0.84)Mn_(0.16)O₂,Li_(1.050)Co_(0.84)Mn_(0.16)O₂, and Li_(1.114)Co_(0.84)Mn_(0.16)O₂.These cathode active materials were prepared according to theco-precipitation method described above. In FIG. 20, groups ofdiffraction patterns are arranged from bottom to top that correspond,respectively, to increasing manganese content, i.e., from 0.04 to 0.10to 0.16. Within each group, however, the lithium to transition-metalratio (i.e., [Li]/[Mn_(x)Co_(1−x)]) decreases in three increments frombottom to top. Reference bars indicating the peaks expected for Li₂MnO₃,Co₃O₄, and LiMnO₂, are shown in pink, grey, and blue colors,respectively.

The cathode active materials in FIG. 20 are mostly single phase. Theabsence of peaks in the vicinity of 2θ=200 indicates the absence ofLi₂MnO₃ in the cathode active materials. Moreover, despite increasingsubstitution of Mn for Co. the crystal structure of each cathode activematerial, as represented by space group, remains at R3m. However, forlow values of [Li]/[Mn_(x)Co_(1−x)], i.e.,Li_(0.975)Co_(0.84)Mn_(0.16)O₂, metal-oxide phases of M₃O₄ stoichiometryemerge (e.g., Co₃O₄).

FIG. 21 presents X-ray powder diffraction patterns for cathode activematerials represented by compositions of Li_(0.994)Co_(0.78)Mn_(0.22)O₂,Li_(1.100)Co_(0.78)Mn_(0.22)O₂, Li_(1.197)Co_(0.78)Mn_(0.22)O₂,Li_(0.973)Co_(0.72)Mn_(0.28)O₂, Li_(1.087)Co_(0.72)Mn_(0.28)O₂,Li_(1.19)Co_(0.72)Mn_(0.28)O₂, and Li_(1.247)Co_(0.72)Mn_(0.28)O₂. Thesecathode active materials were prepared according to the co-precipitationmethod described above. In FIG. 3, groups of diffraction patterns arearranged from bottom to top that correspond, respectively, to increasingmanganese content, i.e., 0.22 and 0.26. Within each group, however, thelithium to transition-metal ratio (i.e., [Li]/[Mn_(x)Co_(1−x)])decreases in three increments from bottom to top. Reference barsindicating the peaks expected for Li₂MnO₃ and Co₃O₄ are shown.

In FIG. 21, the substitution of Mn for Co is higher in than that in FIG.20. However, the crystal structure of each cathode active material, asrepresented by space group, is R3m. Diffraction patterns forLi_(0.994)Co_(0.78)Mn_(0.22)O₂, Li_(1.10)Co_(0.78)Mn_(0.22)O₂,Li_(0.973)Co_(0.72)Mn_(0.28)O₂, and Li_(1.087)Co_(0.72)Mn_(0.28)O₂ showpeaks in the vicinity of 2=200. Such peaks indicate the presence ofsmall proportions of Li₂MnO₃ in these cathode active materials. However,the peaks are not present in cathode active materials represented bycompositions with values of [Li]/[Mn_(x)Co_(1−x)] approaching 1+x, i.e.,Li_(1.197)Co_(0.78)Mn_(0.22)O₂ and Li_(1.247)Co_(0.72)Mn_(0.28)O₂. Theselatter cathode active materials are single phase. The metric 1+xcorresponds to an ideal solid-solution stoichiometry forxLi₂MnO₃.(1−x)LiCoO₂ (i.e., Li_(1+x)Co_(1−x)Mn_(x)O_(2+x)).

Example 16—Cathode Active Materials by Sol-Gel Methods

A first aqueous solution of manganese acetate and cobalt acetate wasprepared at a predetermined molar ratio (i.e., [Mn]:[Co]) and a total of2 mol. As described below, the predetermined ratio includedrepresentative examples such as [Mn]:[Co]=0.10:0.90, 0.16:0.84,0.22:0.78, and 0.28:0.72. A second aqueous solution of 1.0 M citric acidwas added to the first aqueous solution and mixed via magnetic stirringto produce a combined solution. The combined solution was heated to 80°C. to form a gel, which was subsequently kept at 80° C. for 6 hours. Thegel was then transferred into a box furnace and calcined at 350° C. for4 hours. After cooling, the resulting cake was ground by mortar andpestle, sieved, and re-fired at 900° C. in flowing air for 12 hours. Theramp rate was 5° C. per minute, and after firing, the resulting cathodeactive material was allowed to cool in the furnace to ambienttemperature via natural heat losses. Samples of the cathode activematerials were characterized by powder X-ray diffraction using a BrukerD8 (see FIG. 23).

Representative examples of cathode active materials produced by theabove-described sol-gel method include Li_(1.131)Co_(0.90)Mn_(0.10)O₂,Li_(1.198)Co_(0.84)Mn_(0.16)O₂, Li_(1.241)Co_(0.78)Mn_(0.22)O₂, andLi_(1.301)Co_(0.72)Mn_(0.28)O₂.

FIG. 22 presents scanning electron micrographs of cathode activematerials prepared according to the sol-gel method described above. Themicrographs indicate sheet-like agglomerations of fine particles havingdimensions less than 1 μm. Such fine particle morphology is typical forcathode active materials prepared by the sol-gel method. Thecompositions of the cathode active materials correspond toLi_(1.1)Co_(0.1)Al_(0.01)Mg_(0.01)Mn_(0.89)O₂ and isLi_(1.28)Co_(0.258)Al_(0.02)Mg_(0.02)Co_(0.6802).

FIG. 23 presents X-ray powder diffraction patterns for cathode activematerials represented by compositions of Li_(1.131)Co_(0.90)Mn_(0.10)O₂,Li_(1.198)Co_(0.84)Mn_(0.16)O₂, Li_(1.241)Co_(0.78)Mn_(0.22)O₂, andLi_(1.301)Co_(0.72)Mn_(0.28)O₂. These cathode active materials wereprepared according to the sol-gel method described above. The cathodeactive materials are single-phase. The crystal structure of each cathodeactive material, as represented by space group, is R3m. The absence ofpeaks in the vicinity of 2θ=200 indicates the absence of Li₂MnO₃ inthese cathode active materials. Moreover, peak splitting in the vicinityof 2θ=65° indicates a well-crystallized layered structure.

Example 17—Battery Performance

FIG. 24 presents differential capacity curves for cathode activematerials represented by compositions of LiCoO₂,Li_(1.05)Co_(0.96)Mn_(0.04)O₂, Li_(1.05)Co_(0.93)Mn_(0.07)O₂,Li_(1.110)Co_(0.90)Mn_(0.10)O₂, and Li_(1.19)Co_(0.72)Mn_(0.28)O₂ Thesecathode active materials were prepared according to the co-precipitationmethod described above. Measurements of differential capacity were takenof 2032 coin half-cells during a first-cycle charge and discharge at arate of C/5. In FIG. 24, the ordinate indicates magnitudes of dQ/dV andthe abscissa indicates magnitudes of electrochemical potential, orvoltage. An irreversible phase transition peak occurs for LiCoO₂ at apotential of about 4.45 V. However, after substituting Co with Mn, thephase transition shifted to a potential of about 4.55V with reduced peakintensity. Such behavior indicates that substitutions for Co (e.g., Mnsubstituting for Co) can produce cathode active materials of highvoltage stability.

FIG. 25 presents voltage profile curves for cathode active materialsrepresented by compositions of Li_(1.05)Co_(0.96)Mn_(0.04)O₂,Li_(1.05)Co_(0.93)Mn_(0.07)O₂, Li_(1.110)Co_(0.90)Mn_(0.10)O₂ andLi_(1.19)Co_(0.72)Mn_(0.2)O₂. These cathode active materials wereprepared according to the co-precipitation method described above andthen packaged into 2032 coin half-cells. The voltage profile correspondsto a first charge-discharge cycle at a C/10 charge-discharge rate in thevoltage window of 2.75-4.6V. In FIG. 25, the ordinate indicatesmagnitudes of electrochemical potential (i.e., V) for the coin halfcells, and the abscissa indicates magnitudes of storage capacity (i.e.,mAh/g). For all compositions, high specific capacities (i.e., >150mAh/g) and high average voltages (i.e., >3.7V) are achieved. For cathodeactive materials of Li_(1.19)Co_(0.72)Mn_(0.28)O₂, a plateau atapproximately 4.5V in the first charging curve indicates an activationprocess for a Li₂MnO₃-like phase present in the material.

Example 18—Tuning of Battery Performance

It will be appreciated that factors such as substitution for Co (e.g.,Co_(1−y)M_(y)Mn_(x)) and ratios of lithium to Co and its substitutes(i.e., [Li]/[Co_(1−x−y)M_(y)Mn_(x)]) influence the phases present incathode active materials. As evidenced by FIGS. 20-21 and 23, suchfactors may be selected to produce cathode active materials of singlephase (e.g., R3m crystal structure). Moreover, as evidenced by FIGS. 24and 25, such factors may also be selected to improve battery performance(e.g., increase voltage stability).

FIG. 26 presents a contour plot of discharge energy density that varieswith substitution (i.e., Co_(1−x)Mn_(x)) and lithium ratio (i.e.,[Li]/[Co_(1−x)Mn_(x)]). The discharge energy density corresponds tomeasurements from 2032 coin half-cells during at first cycle and takenat a charge-discharge rate of C/10. The contour plot was generated froma combination of sample measurements and predictive modeling. The 2032coin half-cells used cathode active materials prepared according to thesol-gel method described above, where 0≦x≦0.28. In FIG. 26, two regionsare present that indicate high energy density (i.e., >700 Wh/kg): [1] afirst region for Mn content up to about 12% (i.e., x≦0.12) and a ratioup to about 1.15 (i.e., [Li]/[Co_(1−x)Mn_(x)]≦1.15), and [2] a secondregion for Mn content higher than about 25% (i.e., x>0.25) and a ratiohigher than about 1.25 (i.e., [Li]/[Co_(1−x)Mn_(x)]>1.25).

FIG. 27 presents a contour plot of energy retention that varies withsubstitution (i.e., Co_(1−x)Mn_(x)) and lithium ratio (i.e.,[Li]/[Co_(1−x)Mn_(x)]). The energy retention corresponds to measurementsfrom 2032 coin half-cells after 10 cycles and taken at acharge-discharge rate of C/3. The contour plot was generated from acombination of sample measurements and predictive modeling. The 2032coin half-cells used cathode active materials prepared according to thesol-gel method described above, where 0≦x≦0.28. Similar to FIG. 26, tworegions are present in FIG. 27 that indicate high energy density(i.e., >700): [1] a first region for Mn content up to about 12% (i.e.,x≦0.12) and a ratio up to about 1.15 (i.e., [Li]/[Co_(1−x)Mn_(x)]≦1.15),and [2] a second region for Mn content higher than about 25% (i.e.,x>0.25) and a ratio higher than about 1.25 (i.e.,[Li]/[Co_(1−x)Mn_(x)]>1.25).

Example 19

Four samples of Li_(α)Co_(1−x−y)Al_(y)Mn_(x)O_(δ) were made into coincells with a Li metal anode and cycled from 2.75-4.5V at C/5charge/discharge rate. The four samples corresponded to x=0.01, 0.02,0.03, and 0.04 where ac 1.0; y ranged from 0.001-0.003; and δ was about2.0. FIGS. 28 & 29 show plots of the derivative of the differentialcapacity with respect to electrochemical potential (i.e., dQ/dV vs V)illustrating the effect of Mn and Li content on battery cellperformance. During the charge and discharge of a LiCoO₂ cathode, aphase transition from the hexagonal to monoclinic phase takes placebetween 4.0-4.3V (see FIG. 29). The phase transition also occurs for Mnsubstitutions of x=0.01 (see FIG. 28). The phase transition results in avolume expansion of the crystal lattice that may contribute to capacityfade of the electrode. In such situations, the substitution of Mn for Coin proportions greater than x=0.01 mitigates this phase transition, asdemonstrated in FIG. 28 for compositions of x=0.02, 0.03, and 0.04.

The phase transition is also dependent on the Li content in thecompound. When considering Mn substitutions as inLi_(α)Co_(0.97)Mn_(0.03)O₂, the phase transition can be mitigated ifα≧1.0. FIG. 29 illustrates that, as the Li content increases from 0.977to 1.014, the characteristic phase transition peaks in the dQ/dV curvebetween 4.0-4.3V reduce to a flat line for α=1.014.

On the other hand, the benefit of Li excess is limited by its effect onvolumetric energy density and retention. FIG. 30 demonstrates the effectof Li content in Li_(α)Co_(0.97)Mn_(0.03)O₂ on the discharge energyduring cycling between 2.75-4.5 V at a C/5 rate. The stoichiometriccomposition, α=1.003, shows a maximum energy of 754 Wh/g, and losesabout 8% of that energy in 25 cycles.

The Li rich sample (i.e., α=1.014) has a similar maximum but loses 10%of its energy. The sub-stoichiometric compositions (i.e., α<1.0)compositions show lower energies. This behavior and repeated tests with2% Mn (i.e., x=0.02) indicate that the best energy and energy retentionis obtained at a lithium content where α is about 1.00. Thecompositional values for each metal in the materials were determined byhigh precision ICP-OES analysis, with special regard to the measurementof the lithium content (i.e., α).

Similar electrochemical measurements (not shown) also illustrate aneffect of aluminum content on the mitigation of the hexagonal tomonoclinic phase change. As aluminum is substituted into an otherwisefixed composition of Li_(α)Co_(1−x−y)Al_(y)Mn_(x)O_(δ), the phasetransformation is suppressed.

There may be a, x, and y where volumetric energy, energy retention andsuppression of the phase transition occurs. From this examination it isdetermined that any substitution of Mn, Al, and Li, addition or otherelements that can be substituted into the structure at total amounts of≧3% (i.e., x>0.03) will mitigate the hexagonal to monoclinic transitionthat occurs between 4.0-4.3V. It seems that the additions are alsorelated to a sum of their oxidation states, i.e., Mn⁺, Al⁺, and Li⁺should be added up to some level to prevent the phase transition. Thisis because it has been observed that different Li stoichiometries for agiven Mn content are needed to prevent the phase transition.

Example 20

The optimum Mn content (i.e., x) to achieve the greatest volumetricenergy density and energy retention of Mn-substituted LiCoO₂ cyclingbetween 2.75-4.5 V at a C/5 rate is determined to lie between x=0.02 andx=0.04 as illustrated in FIG. 31. Battery cells including threecompositions of x=0.02, 0.03, and 0.04 and containing similar Li and Alcontent were cycled from 2.75 to 4.5 V at a C/5 rate. The compositioncorresponding to x=0.03, although showing slightly lower initial energycompared to x=0.02, demonstrates the highest energy retention.

Example 21—Nuclear Magnetic Resonance

Solid-state ⁶Li nuclear magnetic resonance (NMR) measurements haveidentified Mn—Mn clustering in Li_(α)Co_(1−x)Mn_(x)O_(δ). Whichclustering, would eventually lead to the formation of Li₂MnO₃ as Mn andLi content is increased beyond the phase limit for Li-rich compositions.Without wishing to be held to a particular mechanism or mode of action,Mn clustering stabilized the cathode structure, which can providematerials described herein with high voltage stability as shown in anyelectrochemical tests.

Though HR-XRD and NMR did not show any Li₂MnO₃ formation for thecompositions considered in this work. New phases peaks correspond toLi₂MnO₃ are absent in both HR-XRD and NMR spectra. FIG. 32 shows acomparison of x=0.03 and x=0.04 for Mn-substituted LiCoO₂.Quantification of the NMR at the designated resonances show that theclustering of manganese for x=0.04 is double that for x=0.03, ratherthan the expected 25% increase. Although Mn substitution is consideredto stabilize the LiCoO₂ R3m crystal structure, large Mn clusters tend toincorporate Li into the transition metal (TM) layer, so that when Li isextracted from the crystal structure at higher voltage (4.5V), if Li inthe transition metal layer drops into the lithium layer, vacanciescreated in the transition metal layer are destabilizing to the crystalstructure.

Example 22—Aluminum Addition

Three cathode active materials with the compositionLi_(1.01)Co_(0.97−y)Al_(y)Mn_(0.03)O_(δ) were made, fixing the Li and Mncontent to 1.01 and 0.03, respectively, while varying the Al content to0.077, 0.159 and 0.760 wt. %. The cathode active materials were testedin half-cells, cycling from 2.75-4.5V at a rate of C/5. FIG. 33 showsthat as Al substitution is increased, the discharge energy decreases.However, the energy retention is improved with AI addition, with thelargest substitution of 0.76 wt % Al exhibiting the best dischargeenergy after 25 cycles.

Example 23—Particle Morphology

To achieve stable and high energy densities, cathode active materials ofcomposition of Li_(α)Co_(1−x−y)Al_(y)Mn_(x)O_(δ) can be processed atsufficient temperatures and times such that secondary particles containdense single grains (i.e., primary particles). These dense single grainscan impart high strength to withstand calendaring processes duringelectrode fabrication and battery cell assembly. FIGS. 34A-34B & 35A-35Billustrate the effect of optimum processing to achieve high strengthparticles.

When precursor powders are processed at sufficient temperature and time,the multigrain structure found in FIG. 34A can be further sintered togain larger and stronger grains as in FIG. 34B that are more difficultto crush. This improved strength is demonstrated in FIGS. 35A-35B. Thesize distribution of the precursor powder calcined at 1050° C. (FIG.35A) grows from 18 to 22 μm due to the partial interconnection due tosintering. When the powder is pressed into a pellet and the particlesare crushed under pressure (i.e., a simulation of electrode laminatecalendering), the particle size distribution is reduced into a bimodaldistribution due to the breaking of particle-particle bonds (i.e.,between primary particles) and particle fracture into smaller primarygrains. However, when the temperature at the same processing time israised to 1085° C., large single grains, which have sintered togetherduring processing, break down to the original precursor size, but nofurther. This strength prevents the formation of new surfaces, such assurfaces which are not protected with an Al₂O₃ coating, and are subjectto interaction with the electrolyte.

Example 24—Energy Retention

The calcination temperature not only affects particle strength, but theenergy retention of the cathode active material as an electrode. As thecalcination temperature increases the energy retention also increases toa maximum between 1075-1080° C. (FIG. 36). The change in surface areaafter compacting powder calcined at increasing temperatures stabilizesas the particle strength increases and no new surfaces are exposed dueto crushing particles. FIG. 36 shows the correlation between strength(stabilized surface area change) and energy retention of the cathodeactive material. In FIG. 36, the cathode active material has acomposition where the lithium to transition metal ratio (Li/TM) is 1.01(i.e., α=1.01 and y=0).

The discharge capacity and coulombic efficiency of first cycle of thecathode material is also correlated to the calcination temperature. FIG.37 illustrates this relationship. The initial discharge capacity andeffectively, the initial energy decreases as the calcination temperatureof the material is increased from 1050-1092° C. The coulombic efficiencyis a measure of the amount of Li intercalated back into the cathodeduring the first discharge, showing the fraction of Li that iseliminated from future charge/discharge cycling. The maximum efficiencyoccurs at 1080° C., whereas the capacity while regarding the particlestrength has an optimum 1070-1080° C. This sensitivity of thetemperature of calcination is part of the novelty of the proposedinvention, since it is shown to affect particle strength, energyretention, Li content, cyclability, capacity and energy of the material.

Example 25—Thermal Stability

Along with the high energy of Li-ion battery materials comes theincreased risk of unplanned energy release, e.g., heat that can cause abattery cell to catch fire. Differential scanning calorimetry (DSC) ofcathode active materials charged and exposed to electrolyte helpdetermine the risk of thermal failure. FIG. 38 shows DSC measurements offive Mn-substituted LiCoO₂ compositions from Mn=1-7 mole % (i.e.,x=0.01-0.07). Compared to commercial LCO (i.e., LiCoO₂), the Mn 1%composition (i.e., x=0.01) shows a lower onset temperature to anexothermal reaction evolving more heat. However, as Mn contentincreases, the onset temperature of the reaction increases and the totalheat released is reduced up to Mn 7%. After Mn=4%, onset temperatureincreases, but the heat release of the reaction begins to increaseagain. TABLE 4 enumerates these values. Based on the DSC measurements,the optimum Mn substitution is between Mn 3-4 mole % (i.e.,0.03≦x≦0.04).

TABLE 4 Summary of DSC Measurements 1% Mn 2% Mn 3% Mn 4% Mn 7% Mn SampleChemistry LiCoO₂ (x = 0.01) (x = 0.02) (x = 0.03) (x = 0.04) (x = 0.07)Average Onset Temperature 186° C. 177° C. 196° C. 243° C. 245° C. 250°C. Average Heat Released (50-400° C.) 0.52 J/g 0.57 J/g 0.38 J/g 0.16J/g 0.15 J/g 0.3 J/g

Example 26—Lattice Parameters

The Li content (i.e., α), critical to the performance of the material,is associated with a change in the c-lattice parameter of the crystalstructure varies as shown in FIG. 39. Depending on the Mn content, whichalso increases the c-lattice parameter as Mn is increased, the Licontent will reduce the c-lattice value as Li increases. It also appearsthat capability of the materials to accommodate for excess lithium inthe cathode active material while maintaining the R3m crystal structureincreases with increasing Mn content. This phase diagram of theLiCo_((1−x))MnO₂ system provides a map of the optimum Li additionwithout forming secondary phases.

Example 27—Raman Spectra

The Raman spectra of the layered LiCoO₂ and Mn-substituted LiCoO₂ (i.e.,x=0.04 and 0.07) are shown in FIG. 40. The Raman spectra were obtainedusing 785-nm photonic excitation. According to factor-group analysis,the layered LiCoO₂ with R3m crystal structure is predicted to show twoRaman-active modes, i.e., one at ca. 596 cm⁻¹ with Al_(g) symmetry dueto a symmetric oxygen vibration along the c-axis and one at ca. 486 cm¹with E_(g) symmetry due to two degenerate symmetric oxygen vibrations inthe a/b crystallographic plane. With the addition of Mn into thestructure, new Raman scattering features appear at frequencies above the596 cm⁻¹ band and below the 486 cm⁻¹ band. This new scattering is due toMn—O bond stretching vibrations associated with the various Mn—Co—Lioccupancies that form throughout the transition metal layer. Therelative intensity of the bands caused by these new Mn—O vibrationsincreases with increasing Mn substitution. The band near 320 cm¹ is fromthe CaF₂ window through which the Raman spectra are taken.

Example 28—Stability to Oxidation

The oxidative stability results for 7% Mn substitution (i.e., x=0.07)compared with 4% Mn substitution (i.e., x=0.04) are shown in FIG. 41.Half-cells were charged from an open circuit value to 4.65V and thencycled between 4.0 V and 4.65 V in a continuous cycling run. The 52ndcycle was a full cycle taken between 2.75 to 4.65 V. In FIG. 41, theplot of discharge capacity at 52nd cycle versus lithium to transitionmetal ratio (i.e., α where y=0) shows that the optimum capacity occursat Li content (α) near unity. Compared to x=0.04 under these cyclingconditions, the x=0.07 substitution maintains a higher capacity over 52cycles, which shows better capacity retention under these conditions.

In FIG. 42, the dQ/dV of a half-cell incorporating a cathode activematerial of Li_(1.00)Co_(0.93−y)Al_(y)Mn_(0.007)O_(δ) is plotted withthe dQ/dV of a half-cell incorporating a cathode active material ofLi_(1.025)Co_(0.96−y)Al_(y)Mn_(0.04)O_(δ). FIG. 42 shows that thereduction process for the x=0.07 sample at high voltage occurs atapproximately 4.53V. However, another reduction peak for the x=0.04sample is evident at 4.47 V, which indicates possible instability oradditional phase changes. Such instability or phases changes may lead tostructural transformations with cycling. Note that there is norespective charge peak for this reduction process which could indicateirreversibility and thus inferior capacity retention when cycled tohigher voltages of 4.65 V as discussed in FIG. 41.

Example 29—Capacity and Coulombic Efficiency

The capacity on the first cycle is depicted in FIG. 43 wherein the firstcycle charge and discharge values are plotted as a function of thelithium to transition metal ratio (i.e., α where y=0) along with thecalculated coulombic efficiencies. The improvement in coulombicefficiency is better for near stoichiometric values. The greater α themore Li can be extracted out of the cathode active material. However,and in converse, the higher the Li content, the lower the resultantdischarge capacity. An optimal α is hence investigated.

Example 30—X-Ray Absorption

From X-ray absorption (XAS) results (not shown here), for all compoundsthroughout the series, Co is in the +3 oxidation state and Mn in the +4oxidation state for all a values in the Mn-substituted LiCoO₂ samples.As such, the calculated stoichiometry isLi_(0.983)Co_(0.914)Mn_(0.069)O₂ and Li is deficient in the Li layer.Moving Li cations out from the Li layer to satisfy for transition metallayer leads to Li_(0.966)[Li_(0.017)Co_(0.914)Mn_(0.069)]O₂. (Note thatthe bracketed values for Li, Co, and Mn sum to unity.) For the purposesof this summary we further distinguish this material as having about 5%Li-deficiencies in the Li layer and some small amount of Li in the TMlayer to join with Mn to make Mn—Li—Mn domains in place of Co—Co—Codomains with charge compensation being a key to the stability of theresulting lattice LiMn₂. However, the size of these units is limited assuggested by density functional theory (DFT) total energy calculations(not shown), and shows greater stability in the model as compared tox=0.04 under the above cycling conditions.

The foregoing description, for purposes of explanation, used specificnomenclature to provide a thorough understanding of the describedembodiments. However, it will be apparent to one skilled in the art thatthe specific details are not required in order to practice the describedembodiments. Thus, the foregoing descriptions of the specificembodiments described herein are presented for purposes of illustrationand description. They are not targeted to be exhaustive or to limit theembodiments to the precise forms disclosed. It will be apparent to oneof ordinary skill in the art that many modifications and variations arepossible in view of the above teachings.

We claim:
 1. A compound represented by Formula (III):Li_(α)Co_(1−x)M_(x)Al_(γ)O_(δ)  (III) wherein: M is Mn, 0.95≦α≦1.10,0<x<0.50, 0≦γ≦0.05, and 1.95≦δ≦2.60.
 2. The compound of claim 1, wherein0.01≦γ≦0.03.
 3. The compound of claim 1, wherein 0.02≦γ≦0.03.
 4. Thecompound of claim 1, wherein 0.002≦γ≦0.004.
 5. The compound of claim 1,wherein 0.001≦γ≦0.005.
 6. The compound of claim 1, wherein Al is in anamount of at least 2000 ppm.
 7. The compound of claim 1, wherein Al isin an amount of at least 900 ppm.
 8. The compound of claim 1, wherein Alis in an amount of at least 500 ppm.
 9. The compound of claim 1, whereinthe compound has an R3m crystal.
 10. A compound of Formula (VII):Li_(α)Co_(1−x−y)M_(y)Mn_(x)O_(δ)  (VII) wherein M is at least oneelement selected from the group consisting of B, Na, Mg, Ti, Ca, V, Cr,Fe, Co, Ni, Cu, Zn, Al, Sc, Y, Ga, Zr, Ru, and Mo, 0.95≦α≦1.30,0<x≦0.30, 0≦γ≦0.10, and 1.98≦δ≦2.04.
 11. The compound according to claim10, wherein 0.98≦α≦1.16 and 0<x≦0.16.
 12. The compound according toclaim 11, wherein 0≦γ≦0.05.
 13. The compound according to claim 10,wherein the compound has a single phase.
 14. The compound according toclaim 10, wherein the compound has a trigonal R3m crystal structure. 15.A compound represented by Formula (VIII):Li_(α)Co_(1−x−y)Al_(y)Mn_(x)O_(δ)  (VIII) wherein: 0.95≦α≦1.30,0<x≦0.30, 0≦γ≦0.10, and 1.98≦δ≦2.04.
 16. The formula of claim 15,wherein: 0.96≦α≦1.04, and 0<x≦0.10.
 17. The formula of claim 15,wherein: 0.98≦α≦1.01, 0.02≦x≦0.04, and 0≦γ≦0.03.
 18. The compound ofclaim 15, wherein the compound has a single crystalline phase.
 19. Thecompound of claim 15, wherein the compound has a trigonal R3m crystalstructure.